There has been some recent rumors around TES V that could support this one. According to Todd Howard, the Executive Producer of TES IV: O, Bethesda has been working on a game for the last two years; about the time they were done with Fallout 3. Prior to devoloping Fallout 3, Bethesda said that they'd start making TES V after F3 had shipped. In an interview with Eurogamer, released on Agusust 16th, he stated that "One thing I can say is that from when you first hear about it to when it's out will be the shortest it's been for us. It's pretty far along. When we show it, we want to show a lot, because there's a lot of game there to play right now.
"You know, if Pete Hines came in and said, "I want you to show it," I'd be like, "Okay, I'm ready to show it." But we've just decided for now not to yet."
Shortly after this, around 26th of August, Howard said in a Bethesda podcast that he had been writing "relatively the same type of game for a very long time ... consoles are powerful enough now that we can do some pretty deep, dynamic kind of games". Howard also says that he and the Bethesda development team have been working on the game since they finished Fallout 3. He adds that they are "not ready to talk about it yet but we are really excited with how it looks. I mean, if we were forced to show it right now we'd be proud to show it, but we just don't feel the timing's quite right yet to show it." and "It's the game everybody in the team really wants to play."
Around the time of quakecon, when these rumors first appeared and were commented on by Howard, there was a rumor that the game would be shown then, butultimately weren't.
Link to Eurogamer: http://www.eurogamer.net/articles/2010-08-16-bethesdas-todd-howard-interview
Link to Bethesda Podcast( the one in question is from August 26): http://bethblog.com/podcast/
Thanks to uesp.net.