A class QB is almost always the most important recruit in your class. Langsdorf has done a great job of adding talent, no doubt. Colson would be the most important recruit in this class (IMPO, even moreso than Bookie) - based on pure talent and the position he plays. I have a hard time seeing a scenario where POB and Gebbia both finish their careers at Nebraska...
If Tanner Lee wins the job and plays either a year or two, that would mean a POB vs. Gebbia competition eventually to take over for Lee. The loser of that battle likely transfers since there is only one year separating them. Especially if that ends up being Gebbia, no way (IMPO) POB sticks around if a guy under him beats him out. MAYBE Gebbia stays if he gets beaten out by POB, but I doubt it...
IF POB wins the job over Lee, would Gebbia stick around for the next several years and sit? Maybe the coaches try and sell him on POB leaving early for the pros and Gebbia getting a couple years down the line. Obviously a lot of factors go into that senario...
This is why it is so darn important to bring in a solid, top-of-your-board QB in each class like Langsdorf has done the last two years with POB and Gebbia. Attrition at the QB spot is so common. Nebraska has seen it first-hand over the last decade or so with guys like Harrison Beck, Patrick Witt, Cody Green, Bronson Marsh, Johnny Stanton, Brion Carnes, AJ Bush...not to mention adding guys via transfer like Sam Keller and Tanner Lee. Just because the QB room looks promising now, the flip side of that coin is the attrition that happens when the cream rises to the top.