I think Getty's top photographers are in a far stronger position to resist than microstockers are. It's utterly absurd to try to tell some of the world's most famous photographers that they have to sell their work for 40c a shot.
I bet they were ready to pull out by the hundred and would have sued if Getty tried to hang on to any control over their work.
Interestingly, I see that over on iS, Sean Locke has said "I'm not going to lay out any ultimatums yet, but this [making TS participation compulsory] would be a bad decision for IS". Which sounds almost like the sort of observation a Mafia godfather might make to a wayward nephew.