Personally, I think he'd give 1 more try at making the NFL next year, seeing as he wasn't exactly in top form this past year (coming off wrestling, the motorcycle accident). If he fails, then I think he'd come back at that point.
Off course, if he wants to come back sooner, I'd be all for it. He'd easily be the most over heel in the entire company. I only hope the WWE doesn't job him out right away to "teach him a lesson", *especially* to Taker/HHH/Orton.