Why not? They released SC2 and a WoW expansion this year. I'd doubt they'd be released the same quarter, but an expansion and a new game in the same year isn't exactly unfeasible. If they move the SC2 expansion to quarter 3, it'd be available roughly a year after SC2, which is reasonable, and then they'd get boatloads of xmas sales for Diablo
Its just a XPAC for SC2! Diablo will be the hit for them in that year!
I think the "MMOFPS" thing is just rumormongering really. Whatever Blizzard may say about their project, they fully intend for it to wholly replace WoW. Notice how there are no wow expansions slated after #5? The traditional fantasy / rpg elements work best with the MMO genre. Blizzard knows this. WoW wouldn't have nearly the wide-scope appeal it does now if it were something like Halo.
This isn't to say the new MMO won't be something completely new and separate from WoW, I just highly doubt it will leave the RPG genre. Maybe edge out a bit on fantasy but it will probably still be an RPG at its roots. But that's just me.
While Titan is a good name.. and a MMOFPS is likely... and a partnership with Bungie.. is likely (via Titan and via Battle.net 3rd partners). this leak is not a leak its fan made blizzard would NEVER i repeat NEVER use a ugly green Color or font like that.
blizzard is better than this. ... but i do want to play there next mmo NOW!