MLS is slowly transitioning from a retirement league to a farm league.
Guadalajara recently just sucked what few decent players Chivas USA had down to Mexico and replaced them with hot basura. If Chivas USA ownership actually invested in the team they could be the Bilbao of the MLS.
With Yankee/Man City NYCFC team coming soon, I predict they will be a US based farm team for Man City.
MLS needs to make some strides in making it a league that can stand on its own. I think though Don Garber plays a roll, the teams themselves have to perform at a level where they can get respect from fans domestically and from clubs internationally.
Though many say there are tons of systemic and infrastructural things that need to be done before this, I think the MLS should figure out how to establish promotion and relegation. That is truly the only thing that will light a fire under many teams butts IMO. Perhaps they could buy or absorb NASL and USL Pro to make a second and third tier. The only other way would be for the MLS to set up it's own second and third tiers and lure talent from NASL and USL over to MLS 2 &3 as the contracts are owned by the league and not the teams.