My understanding is MLS takes a block of seats (apparently west side lower bowl) for themselves - so the delay is figuring out how to reallocate tickets to those SSH who will be affected.
Ergo, all SSH will have first crack at tickets, just a few will have to move around. Which is no different from other major sporting events (ie when the Jays made the WS the entire 100 level in LF turned into a media press box etc)
Also the tickets made available to Seattle supporters were $94-99 CAD, so I'm holding out hope the prices are similar to the first three matches.