Lynch is 28. So after this season he'll be 29 (bday is in April).
It all depends on his play obviously, and Michael and Turbin. Everyone thinks Michael will be the future of this team. Dude has moves. But we got to see if his skills actually translate onto the field during gameday. If he has some good games this year and looks like he can be the man, then yeah, Lynch could be gone. But if he looks average or whatever they could need lynch for another year (they would have to restructure his contract probably, who knows how that would go. Its all speculation at this point).