I've heard a large amount of rumors concerning Blizzard's new MMO over the last couple years and very few facts. What little information we do have is based on vague developer interviews and logical assumptions. It's frustrating not to have any details, but I can understand why Blizzard is holding onto secrecy for as long as it can. The premature advertising blitz of several recent games has been blamed for creating an environment of hyperbole which raises player expectations too high. These games tend to have an impressive amount of initial box sales, but disappointing subscription numbers. Another reason Blizzard might be keeping quiet is that there are a large number of World of Warcraft clones in existence. You could be pretty sure that Blizzard's new MMO will have a similar wave of poorly implemented imitators.
Not that World of Warcraft started off as a unique snowflake of a game. In fact the only new thing that Blizzard brought to the MMO marked with World of Warcraft was a sense of polish. However, it was such a difference from the poorly implemented and buggy competition that World of Warcraft turned into the monster we have now. With Blizzard's new MMO we can probably expect the same trick just with a different "type" of MMO. That's why
reports that Blizzard's new MMO will be a hybrid first person shooter sound credulous to me. There's been three or four games that tried mixing elements of FPS games with the persistency of a MMO. None have experienced anything resembling success though and there seems to be a problem getting the right mix of features from each genre. It would take a company like Blizzard with a mantra of "as long as it takes" to pull it off I think.
Also the rumour of a FPS MMO does seem to match what little information we have on Blizzard's next game.
1) It has a more sci-fi then fantasy setting
2) It's not based on an existing Blizzard license
3) It will be a very different game from World of Warcraft
Then again there are probably a dozen other rumors that also fit the sparse "facts" we have. There's a high chance that
NoFrag simply chose a rumour at random and ran a news snippet claiming an inside source had confirmed it for them. I'm sure they got a nice boost in traffic from the story. I expect we might find out the truth at this year's Blizzcon and other bloggers have the same thought on the matter. One thing that I haven't seen pointed out though is that the expanded leaderboard and matchmaking functionality of the new .BattleNet would integrate well with a FPS MMO. Just an observation though.