I think the biggest potential problem is if they go a bit linearity/setpiece heavy. That was a frequent complaint about the last Hitman (which is about as close to Thief as Eidos has gotten property wise) and it was somewhat justified. But since the game was long and still had plenty of open areas I didn't feel the need to bitch that occasionally you're running down hallways from a bunch of pursuers, with less spots to hide (and they're usually just there so you can slip off and make it easier to run later). I suspect either way that the purists are going to be angry about a couple scripted sequences and such though.
Wait, did you just call me a dudebro?
Actually, the biggest AC fans I've met offline were all women.
Apparently chicks really dig pirates and Ezio.
Not big on indians and arabs though.