In villages, when there has been a stronghold under the well in previous versions, now the part of the well above ground is replaced by a staircase. Digging underground reveals that the stronghold itself is gone.
I've attached a couple of screenshots of the seed "root". One is what it looks like in 0.14.3 on Win10; the second is what it looks like in 0.15.0 in PE.
I haven't confirmed if this applies to strongholds which are not under villages
rplatham update for 0.16.0 Beta build 1: trying to generate a new world with a village with a stronghold within render distance crashes MCPE when the generating terrain bar is 1/2 way completed. Try seed 228529541 for example. However, seed robot does generates without crashing (stronghold is still messed up, just a small staircase under the well).