It depends on what they want to do with the Sylvanas Warchief project. As it looks now, the honourable Orcs are incompatible with the way Sylvanas does things.
Therefore, that makes the possibility of defecting Orcs a bit higher than usual.
I personally believe Saurfang will be like Vol'jin 2.0. In other words, he might forge a pact with Anduin to overthrow Sylvanas, but not really defect in the end.