I'm pretty sure at this point the release is locked and they can't delay it. To be honest I'm not worried about content as much as I am with overall polish.
This may be a personal thing, but when I look at the UI in the latest HOMM and then at the UI in King's Bounty, I'd say a lot more care went into making the King's Bounty UI good and pleasant to look at. By contrast, HOMM's is functional and that's about all you can say for it. The same is currently true with Elemental. It gets the job done, but that's as much as I can say about it.
There are other minor polish issues that add up, too. Things like if you win you still have to end your turn before it shows you that you won because the engine evaluates everything at beginning of turn, not being able to exit from city build mode by clicking outside the city, weird options (even if I uncheck "Enable Music", it still plays until I uncheck "Enable Layered Music"), not being able to load a game in the middle of one...
So my main worry now is that they'll spend most of their time on content and the remaining features, and not have any to give the game the polish it needs.