Inoki is already completed and 100% Playable, I think in the ballpark of two weeks ago.
We more than a few new Puro grapplers ready to go.
Don't expect too many new features in 5.5. Some bug squashes, moveset/texture/attire updates, arenas. After that we're squashing a lot of DLC and going to work on 6.0.
I wouldn't expect to see 6.0 anytime soon. We'll shove out 5.5 and get to work on making this a true sequel. Dynamic tag teams and rivalries will BE A THING in 6.0. It's just going to take an incredible amount of time to write. Managers, as well.
The roster will be evaluated and the team is going to discuss who stays/who goes. Rivalries will change the way the computer reacts towards each other. For instance, if Triple H is fighting Joe Shmoe, he'll have his normal A.I. If he's in a match against Cactus Jack, he'll use a lot more weapons/rough style.
Different tag teams will have different bonuses. If you play as The Hardys, your health is increased along with the damage your torso can take.
If you play as DX, I do believe I've devised a way to make the taunts tag-team specific. therefor, Shawn and Trips will crotch chop, but only as a tag team (along with other bonuses).
We will have Poly-Hacked models. I don't know how many. Don't ask. 1 is what we have so far (thanks to Jordy) and it's MORE than enough.
Certain Wrestlers will have "Intimidate" which gives them special bonuses for taunting while in special. More to come on that.
New arenas. Probably all around. Backstage fights will return. Storymode will be looked into.
Remember: you are seriously going to wait a long time for it. No lie. Enjoy the next download when it comes because it's the last for along time unless you guys make it yourselves.