That seems like an awfully silly thing to say given what Charlie Ward did at FSU. Obviously Charlie Ward was a pretty unique talent but to say it isn't going to happen is ridiculous. (For anyone that does not know what Charlie Ward did, he won the Heisman as FSU's quarterback and played pg, ultimately playing professional basketball) It has happened in the past at big time football schools and it could happen in the future. Furthermore, players at OU during the Stoops era have played two sports. At least one played football and baseball and another played football and ran track (Blanton (I think that was his name) ulimately quit football to solely run tract).
If you need another example of guys being stars at two sports Danny Ainge and Dave Logan are other examples. Logan was actually drafted in the NFL, NBA and MLB coming out of CU.
http://en.wikipedia.org/wiki/Dave_Logan_(American_football)