The Ali Act bans exclusive contracts. So, the UFC would cease to function as a league. It would just end up being a promoter, and nothing else.
2 possible futures of the sport under the Ali Act:
1) It would end up like boxing where fighters fight under like 5 different world title belt systems, divided among dozens of different promoters, and weight classes for 'champions' every 5 lbs.
2) The alternative possible future is it would just drive the creation of a UFC type league outside of the US.
So, either it turns MMA into boxing or it just moves the MMA industry outside of the country.