This will turn them into a "secret" society. They will still practice the religion underground.
Back to the Illuminati perhaps? A secret handshake and a trouser leg rolled up before the final prayer at the KH. hehe.
Banning a religion strengthens their religious fervour - they all like a bit of persecution - it keeps them keen, gives good PR to the world and keeps members in other countries on their toes. As to money, they will consolidate their affairs in Russia, perhaps appeal with the help of the UN or some other religious freedom orgs and rake in the donations from JWs world wide. Perhaps setup a seperate contribution box, like they did for Malawi (I seem to remember).