The TA probably didn't know, or wasn't experienced enough to have dealt with them before. Sunquest MIGHT pull through, however if they don't, they will provide you an option (usually split the group into different departure cities, and different dates, and will honor pricing if you stick with them). If it's unacceptable for you then yes, it's a matter of rebooking with whatever tour operator/price is available at the time. This happens when Sunquest gets their confirmed space with WJ which is about 4-5 months before travel..so long ways off.
Sorry for all your stress!! I would say if Sunquest is using WJ flights, that it's safe to keep around 30 on Sunquest, and book the other 30 with WJV and you should be fine. Also, if people are from different cities and it's 2 from Van, 2 from Toronto etc..don't worry about them, just be careful about large groups (30+) from one city.