will they be forced to relegate?
This is just my belief, but I think the 2-year limit ascension teams get is to test to see if the orgs would be financially stable to remain in a partnership. Riot will probably expand the leagues in the future, but doesn't want to commit to bringing in new orgs when they don't know how stable they are. It wouldn't make sense for Riot to not expand the league, the game's getting more and more popular, and having small tournaments with few teams is just making them lose fans, viewership, and brand recognition that they could be getting.