If they go back to using the Drachma it will happen quicklt, then they can start making large withdrawals from their bank accounts (after a 30% haircut for a bail in). It won't be long before they can start accumulating Bitcoin, and they will probably drive up the volume on exchanges to unheard of levels.
Drachma will be almost worthless if they change to it, as I've read... So they won't probably spend that much drachma on bitcoins. But I'm just speculating, it can happen otherwise. And about that 30% cut, I've been reading about that on that here on the forums, where did that news came from?