In the end, the Bills will have 7 linemen active on game days: 5 starters + 1 "swing" tackle and 1 G/C backup. If Henderson continues to improve then I think he would be a strong candidate for swing tackle. The staff seems to see Hairston as a guard now (and I'm not sure he's even going to be around with his recurring back problems) and Kouandjo has been slow out of the gate.
This is a legitimate thought, IMO- especially since no one seems to be grabbing hold of the RG position. However tackles typically only get moved inside at the ends of their careers or when the coaching staff decides that they can't cut it at OT, and I don't expect them to come to that conclusion about Kouandjo until next season (at the earliest), if at all.