The major thing is that based don't actually matter in Age of Sigmar. The round bases are far more for ascetic then any real rules mechanic. I can see them testing some rules from AoS, or perhaps bringing in things like the subfaction rules.
I do have some small concerns that the Old World is quickly going to run into the problem Fantasy, AoS and 40k have, which is that they introduce so much stuff that it takes forever to update anything. End up with so many factions, none of them get a particularly decent work. Or worse, they get a good introduction/first wave, and then sit years without any follow ups. Fyreslayers, Brets, etc.