Bethesda now have two IPs which gives the company more flexiblity. Therefore, the most efficient strategy is probably to release TESV for this generation of consoles and FO4 for the next generation of consoles. Personally, I expect TESV to become available close to early 2012 and FO4 close to late 2014.
My thoughts exactly. Also, if they alternate one title then another (at least until they get a big enough team to develop both at once) then that can douse any specter of favoritism. I can see it now, if they made two of one IP in a row, the other fanbase would explode with (warning: satirical webspeak ahead): "OH NO3S T3Y R LAVING TEH SERIES 4 TEH STUPID 1!!!!1!!!!"
Don't say it won't happen, you know it will. So if they go Oblivion-Fallout 3-TESV-Fallout 4- and so on, then people can just say "well, no, they're just currently on series A or B" whenever that comes up.
As for QuakeCon, it was a full year since last year's QuakeCon misquote. So I think if they say anything at all, it will be so direct and explicit a statement as to make it impossible to misquote. Which is to say either they will say nothing or announce it outright.