As confirmed at a James Bond press conference today, and later relayed by 007's Twitter (naturally), the title and villain rumors were true: Bond 23's official title is indeed Skyfall, and Javier Bardem is our villain. Additionally, director Sam Mendes has now made clear that Skyfall is a self-contained story that "doesn't connect with the last two movies," so if you still haven't sorted out what a "Quantum of Solace" is, don't even bother now. It will not affect your Skyfall experience.
Here's the film's vague official synopsis:
Bond's loyalty to M is tested as her past comes back to haunt her. As MI6 comes under attack, 007 must track down and destroy the threat, no matter how personal the cost.
How that loose premise ties into Bardem's role or the Skyfall title remains unclear, but producers Michael G. Wilson and Barbara Broccoli claim the name has "some emotional context," so... I don't know. Something emotional. Maybe Bond's dog dies, and Bond's dog is named "Skyfall." Perhaps M will be found out for trying to quietly replace Skyfall with another dog that looks a lot like Skyfall, except, what is this spot on his tail? Wait a minute... This isn't Skyfall. What happened to ol' Skyfie, M? No... say it isn't so. Javier Bardem will pay for not being more careful backing out of the MI6 driveway.