Well lets say its 2027 and that when this happens...
The CPL salary floor would have risen to at least 3M based on recent trends.
The incentive would be that the MLS teams would be allowed to have salary flexibility. (Well I guess Forge could join them aswell). The teams would continue to look the way they do now, it just the Canadian players would get a lot more minutes. At the moment there's a massive budget gap, but I can't say there's a massive talent gap, and I think at some point the CPL will introduce a marquee or designated player that would help with the merge.
The fan bases I don't believe will be effected. I don't think they are so embedded into the MLS (most don't even know the rules) that they would notice the difference other than Gareth Bale not coming to Montreal. Considering Montreal and Vancouver have had fan bases that have existed long before the MLS I don't think it will have the negative effect people like to think. There's Eurosnob, is Americansnob a thing? I hope not. I think people overhype the Toronto vs insert big American city. Those opportunities would continue to come in the expanded CCL which would provide greater opportunities for the bigger clubs (TFC, MTL, WFC) to continue to be on the continental stage vs having to compete for essentially 1 guaranteed spot (VC Champion).