If my choices were between doing a double-take when seeing it on a store shelf, or seeing something online to the effect of, "TES5 in development, targeting fall of 2012 for release," I'd have to side with the complete surprise option.
By either seeing it on a shelf, or hearing that it's being made, I'd be equally ecstatic. One way, I'd get to go home and start playing it, and the other way I'd have to wait two years while being routinely teased with it. Yup, easy call.