I don't know that I would say "hemorhage". It would lose some, to be sure.
I would imagine that a lot of those who leave would be those who claim they don't like the politics. So they will leave and join some apolitical religion. Which will suck, because only the politically active religions are interesting to the players, despite what they claim. And it will die on the vine. And we'll be back to SA...
I agree, boring religions die fast. But if there were some hypothetical second religion that had clout and promised ultimate power, wealth, virgins, etc., I think SA would certainly significantly sink for the convenience factor. Ismail, as a perennial pragmatist would probably consider jumping ship if it would benefit him, though he would never admit that, eve to himself. Honor and all that!
It would be cool to see some religious movement sweep the south and unite all the smaller religions, but I don't really know what could accomplish that. I'm enjoying the fundamentalism of the Bloodspeakers on BT, maybe some similar grand old pagan revival could unite against SA and provide a viable counterweight.
Hmm, I wonder what would happen if CoB, VE and AP had lovechildren...