I am asking because there is space for exactly 48 prophecies available under the prophecies tab.
Or is 48 the maximum number of open accepted profecies?
Having finished my first propecy I can answer my question myself.
The 48 slots are for prophecy you accepted/bought. Once it is fulfilled the slot is emptied, making room for another one.
So there is no limit, but perhaps a limit for the number of concurrent active prophecies.