I kind of doubt we'll get new mechanics at this point in the game - general consensus seems to be that Frontier actively supports (most) games for about 3 years and we're heading to that point. The engine itself is starting to show it's age and limitations, they no longer have a large development team, etc. My best guess is that they are going to finish fine tuning the burrowing and diving mechanics (add more animals to those abilities), and finish up adding whatever animals they consider necessary for the remainder of the game's lifecycle. I don't get the impression that the game is making so much money that they'd go out of their normal cycle to extend work on this game, and even if they were - as I mentioned above, the game's underlying engine and mechanics are becoming dated (single threading being the largest obstacle to increasing game complexity). They might add some larger habitat birds that traditionally in zoos and are not always in roofed enclosures (cranes, flamingos, other large birds of various sorts), as part of their standard packs moving forward. I certainly doubt they'd also do a major overhaul of animal behaviors or animal care needs on top of it, so whatever birds we did/do get will have the same simplistic requirement sets as any other habitat species.
In a more communicative world, it'd be nice if Frontier said something like - well, free flying is too much work for a game this old/etc, sorry, maybe next time. Or no free flying but we'll be adding more larger birds or whatever. I know that's not their style and I'm not sure why they are so leery about transparency but I think that's due to them being an older game company, and no longer a start-up.
In a more communicative world, it'd be nice if Frontier said something like - well, free flying is too much work for a game this old/etc, sorry, maybe next time. Or no free flying but we'll be adding more larger birds or whatever. I know that's not their style and I'm not sure why they are so leery about transparency but I think that's due to them being an older game company, and no longer a start-up.