He will come back because he is a competitor. However, given the circumstances you are correct.
1. Oklahoma WILL NOT play for the National Championship
2. Oklahoma will likely NOT play for the Big 12 Championship
3. Jermaine Gresham is out for the year and has already said he is NOT coming back
4. Ryan Browles, leading WR, has a broken shoulder and is out indefinately
5. The offensive line isnt what it used to be
6. He is months away from millions of dollars