The South End roof at BMO is about to be put up (via twitter):
Word is that 30,000 is just the initial buildout and the extra space beneath the roof on a couple sides and the wide open North Side is to allow for expansion up to 40,000 eventually (not just temp seats) in the long term. Once that capacity is reached (40k average attendance within 15 years is realistic) we may even see TFC moving into a bigger stadium (60k base, expandable to 80k) either at the same site or somewhere else like the Portlands.