They've been backpedaling a bit on RE6 since its initial release and in talking about future direction, so I'm not sure how much of it will carry over.
It's safe to assume that they'll continue the action route, and iirc they've said as much. Whether or not it will be at the same level or higher is debatable, given that they've also spoken of reinforcing the horror and atmosphere elements ofrom the series alongside it. This has been said in the past between the development of RE5 and RE6, so take that with skepticism.
Co-op is in the bag. The series has always played with multiple playable characters, and co-op was part of their successful marketing campaigns of RE5 and RE6. The number of characters will likely be decreased to two pairs or just a single pair again.
Mercs still in.
The marked difference, at least hopefully, that I can expect is a much tighter and polished game with a clearer focus. It's likely to be its own experience as well, instead of trying to copy moments of past titles.
I want to clarify something, I don't expect Resident Evil 7 to not be an action game of some kind, I guess it's just debatable of what KIND of action game. Like, is this game going to be action-adventure more-so and increase the adventure game elements? Is it going to go bombastic like RE6 or beyond? Is it going to tone down the bombastic and go for a more atmospheric kind? There is no way in hell they are ditching co-op, and to be honest I am 100% okay with that, I like co-op games, and I think they know part of the reason for the recent series success is due to the co-op functionality.
This said, I'm not quite sure they're going RE6-2 or anything. They may make a completely new set of mechanics, or streamline it a bit. I don't know why, but I'm painted with an impression they're really trying to shake up the foundation of the series again, ala' from RE3/Code Veronica > RE4. I think Capcom have more than anything within the last few years talked about "examining the series" in terms of RE, and trying to think how to modernize & realize things about it to a broad audience while also appealing to long-time fans. Capcom even went out of their way to say they need to observe less of what other series are doing, and more what they can do for the legacy and continued success of their franchise.
I guess I'm painted with the impression than RE7 is going to be them trying to do a new take at the series again, but something that's trying to capture what they think older fans wants while also appealing to that broader audience. So I think gunplay will be in it, and be important, and I think co-op isn't going anywhere, but I'm kind of expecting the bombastic to be shifted down a tad from RE6 and them to be trying to go in some more Gothic Horror direction. I partially say this since they kept on describing RE6 as such before release, and they acknowledge Leon's campaign was received the best by most, along with the surprise successes of REmake HD and the Revelations games I guess.
Do I expect it to be scary? Not really... But I guess my expectations are:
-They're going to try and reinvent the wheel a bit again. How successfully is to be seen.
-The game is going to be an action game with co-op.
-...HOWEVER, I think it may be at least trying to be more atmospheric and horror-y than either RE5/RE6, to what extent and what Capcom considers to be horror is out there, though. At the very least I think it'll come off as being much darker.
-I think it'll be scaled back to one or two campaigns, and probably more polished. I get the impression that the biggest thing they pulled from RE6 was it being bloated and not really refined; RE6 had the biggest staff for any Capcom project ever working on it, and they developed it relatively quickly after RE5 (the game came out something like 2-3 years after it started development), Capcom had said they wanted to quicken production of its titles, but evidently that didn't go through with RE7. RE7 seems it'll release four years after it started development, which implies either they've taken a lot of time to refine it, which RE6 didn't get, or maybe they did the classic RE thing of scrapping a whole build or big parts of it and starting again to go in a different direction. At the very least, I do think this will be a much more polished title than RE6.
It's to see what exactly they have cooked up, but those are my expectations. And since RE is basically well known for its bonus content at this point, you can bet there will be bonus content.