The markets have to decide. We can end up with 2 splitted chains with 2 different values, ABC will be the most valuable according to futures, so CSW will try to devalue it with attacks
Even if SV's hashpower was equal, SV would be inclined to mine their own transactions and keep new block time as close as possible to 10 min instead of using their wasting it on ABC
Orphaning would only happen if SV's hashpower >= ABC thereby allowing SV to mine empty/erroneous blocks quicker than ABC hence forming the longest proof of work chain. Seems unlikely