So, when the rumors first dropped, I was pretty concerned. Like everyone.
As more rumors drop, I'm becoming less concerned.
Let's start with the big ones, which are also the early ones.
Unbound, Random-Who-Knows-With-Random-Value-Even Missions, Psychic Phase
First and foremost, NO MATTER WHAT THESE ARE, if any of them are obviously egregious in their impacts on an all-comers open tournament environment, many of them are very clearly "packaged" instead of "infused throughout the game." What this means is you can easily eliminate these things from tournament play if they are genuinely unready for fair fightin' prime time.
It is possible that Unbound armies will be so restricted by rules buffs to Battle-Forged or rules nerfs to Unbound that it is completely reasonable to play with them against each other and without opponent permission. I find this highly unlikely, for reasons that would require their own post. Anyone with enough Apoc games under their belt, however, will remember what people start to do if they get too serious about Apoc or feel like trolling. Nobody wants to have to deal with 40 individual missile/flamer crisis suits.
It's not about people spamming multiples of really expensive killy units that causes problems with the Unbound scenario. It's about people spamming ridiculous quantities of units in a game where MOST units can't target multiple things per turn. In the immortal words of Sweet Georgia Brown ... "Ain't Nobody Got Time for That."
Nevertheless, if Unbound is perfectly implemented, we can use it. If it's as bad as some are concerned it might be for a tournament environment where you can't pre-discuss what's OK or not to bring with each opponent, we simply don't have to activate this module of the rules.
Malestrom of War Missions
Tactical flexibility on the part of a player is good. There's also merit to points accrued throughout the game, as we've seen with the widespread success of the Indy Mission Catalog (missioncatalog.com). What you won't see a lot of people enjoying with time is a set of entirely random missions, where you don't even know your primary until the game starts and you find out whether you deployed well for the missions at hand. There's more to be seen here, and they might be more brilliant than the rumors indicate, but the long and short is we can - again - stick with (As tournaments always do anyway) tourney-built missions evoking some of the spirit of the rulebook missions. Just like with Unbound, these aren't inherent to the game (even the eternal war missions are all still active / in there). They are optional items for all intents and purposes.
The Psychic Phase
So the Fantasy Magic Phase is coming to 40K ... sorta. It's actually much easier / more laid back I think than Fantasy in terms of how it sounds.
There are a LOT of people writing about this so far, as if they have all the details. Questions are still unanswered that define EVERYTHING, such as "can you cast the same power multiple times?" The way the mechanic looks to work, even a non-psychic army has an OK chance to stack all their dice against a single major power cast. I.E., if you want to stop Fortune or Hallucinate or something that will totally determine the following turn(s). Your ability to do so will be further buffed by having psykers of your own. If you can now cast the same power multiple times, however, that is a pretty important piece of information to have - it might argue for powers getting even more meaningful in the game.
One thing I do feel is that on FACE VALUE, key gamebreaking powers oriented around supercharging single units are going to be suppressed in reliability and thus see less time on the tournament tabletop. Generally speaking, if I can stack a few psykers via allies or primary into my army and focus on stopping you from fortuning up or otherwise super-buffing a deathstar, even if that means your other powers go off unabated, that's an OK trade in most books. We'll see how it turns out, but I wouldn't be all that worried.
We don't know enough about everything else to panic, but I don't think we should panic regardless. I do think you should panic if you're holding off on registering for NOVA still ... we're well under half our 40K GT spots left. Similar trends are occurring in most other game systems. ;)
Games Workshop has a history of "striking out" with a few rules every edition. Also, like at the beginning of 6th, new ideas like Battle Brothers are sorta stress tested through their internal processes against the current meta. Battle Bro super stars didn't really become a problem until a confluence of codices that post-dated their edition release. Good point I heard someone make in person last night: you'll note they were clear about GK not being Battle Bro with anyone, thus preventing various grenades and psy buffs being contributed to every Imperial Army. It's the lack of clear QC on a lot of what they subsequently do that seems to create problems and evince weaknesses in edition design.
So the cool thing is - no matter what the new edition is, it's going to probably be pretty fun and interesting right away. Not only will everyone be trying to figure out what is or isn't any good, but that lack of established meta will keep the game pretty wide open. I'm excited to try and attend a couple tournaments in the first 4-6 months again. The potentially uncool things are ... 1) the internet rage and banal commentary that always accompanies change, where blind advocates of the new belittle those who question changes, and where blind advocates of the old strike out universally at all things 7th ... and 2) the slow revelation of what the design studio "missed" with their implementation of rules fixes and brand new rules, potentially conflated by the release of future codices that exacerbate unforseen loopholes.
So it's sorta 40K as we've always known it. It'll be mostly a really fun time, in a game that's so heterogeneous in list / balance / etc., it creates a fairly interesting and intriguing competitive scene for the tourney-minded. Social gaming groups that either like to play one-off games or establish narratives / campaigns are also going to continue to have a blast, because like Tournament Organizers they'll establish rules and regulations to smooth out the rough edges of the game and their impact on fun. I'm a little concerned about Joe Shmoe the LGS hobbyist who hopes to get a few pick-up games in once a week or so, and the squabbles and challenges he may face with Mr. "Unbound's Legal I'm Allowed To!" and his 45 single crisis suits ... but, for most of the folks who read this blog, that's less of an issue I suppose. We have our tournaments, we have our groups of friends, and so we have the dawn of the next edition in a very fun game.