I think they will be allowed (if tests will indeed reveal they do not interfere with "vital aircraft systems", contrary to what we heard every time aircraft doors close). investments are not huge and installing node in aircraft will allow a/c to charge exorbitant fees for roaming.
I wonder if they will have to register as a telecom provider (United Wireless ) - probably they do.

2nd possibility is that technology will go forward by incorporating Wi-Fi capability into the cell phones which will allow to use wireless which is already there (actually now one can make calls from wi-fi enabled planes using your laptop and headset). I'd bet on this option in a long run.

Ax