I had this information when new IITs were announced. It was mentioned very clearly that IT BHU will be given IIT Status.

I have so far not found any rule which prohibits for creating more IITs in one state. I think Roorkee was given IIT status in the year 2000 itself when it was under U.P. Therefoer UP having two IIts i.e Kanpur and Roorkee.( I am not very sure abouit it)