It's a 50/50 shot if you ask me. Blizzard has put Diablo on a console before, and now with pressure from Activision (pretty big money whore), it wouldn't surprise me one bit. I really don't think it would compromise the game too much since it doesn't look like it will need ridiculously high specs.
Blizzard never ported a to consoles. The porting was always outsourced.
One of Vivendi's concerns was to keep Blizzard through independent management after the merge, and Activision assured Blizzard would continue to function the same as always.
Activision's main reason for the merge with Vivendi was to stregthen their PC support, since Vivendi possessed 2 of the most recognized names of the PC gaming industry: Blizzard and Sierra. Actually, Activision also stated that the only thing they want from Blizzard is to release atleast 1 Big Title every year.
Do not over-estimate the control Activision has over Blizzard. Remember that at the end of the day it was Activision that got bought by Vivendi. Blizzard has always been very autonomous in the past, and will continue to be so in the future. When you put out gigantic blockbusters like WoW every few years and earn your owners a few billion dollars then you get a lot of say in how you are managed. It will all depend on what Blizzard wants to do with the game. If there is a port, it will be done by someone else and probably not be very good.
It was Vivendi that bought part of Activision, and holds the majority ownership of Activision Blizzard. Vivendi is 10 times bigger than Activision, and owns several TV Channels, part of NBC, part of Universal Studios, part of Universal Music Group, etc...
I have no doubt that Blizzard will keep doing things like they've always done.