I think we'd all like to see Roger return, but CBS would NEVER let that happen. CBS likes Drew, they implemented some of the changes we've seen in the last 12 years, it wasn't all Mike. As long as Drew is there, I don't think the show would change much if at all under someone else, but there's always speculation of whether Drew would want to continue the show with someone else as EP.
TPIR has had a few EP changes in the Barker era, and while us die hard fans could pick apart the changes done with the EPs, anyone else would hardly notice.
I am gonna go out on a limb and saw that Drew will NOT become the new EP. I don't think he would want that title officially, even though he already has a lot of say about how to conduct the show. If anything, someone already there will be promoted, and it'll be business as usual.