He will not enter himself into the draft; The Lions will not be able to draft him (fortunately).
Is it possible that wind came down that he would end up a Lion and thus decided to stay at Oklahoma?
Honestly, with the direction of the organization completely up in the air while sticking with the same two guys that were here for 0 and 16, there is a reasonable possiblity. The Lions must look like career suicide! Even though you have a Calvin Johnson, there is no protection at this point and it is nearly impossible for a QB to thrive in this current system.