Besides the whole argument of when "summer" or any other season actually occurs...

I think after summer is a good time for it. I'm assuming it's not just going to be visiting other DCs but doing content with other DCs too(maybe a queue merge?). To me, after summer when people start focusing on work more or go back to school is the perfect time for it.

I don't know if anyone remembers queueing for alliance raids or frontlines during the fall/spring during the patches in between expansions, but usually, there'd only be about 8-10 hours worth of time where you could queue into those(at least on Crystal). When I first started it took me three days to get into the three alliance raids required for MSQ because I was logging in too late in the evening(basically had to wait for the weekend). If Cross DC also merges the queue, maybe it won't be so bad.