I'm betting it will take longer than that. Unless you are in a front seat and quite familiar with MCO, by the time your plane lands and you deplane and find your way to transportation and "sign-in", it will be half an hour.
In all honesty, unless the stars and moon align, it's going to take 45 minutes for them to load the bus and get moving. When you're dealing with families with kids, strollers that have to be folded and stowed, possibly elderly Aunt Edwina who takes five minutes to climb aboard, etc., this is not going to be like hopping into a cab and zipping away.
Once you get on the road, it's a full half hour to WDW, and they will go to up to four resorts per bus, so if yours is last, it could be half an hour by the time you make it to WDW property until you're getting off the bus.
So now you've landed at your resort. Even if there's not a long line, remember that potentially five other parties have arrived there with you, so you might have to wait ten, fifteen, even thirty minutes to check-in.
Then you need to account for getting to MGM, which unless you are going to the BWV and can walk there in fifteen minutes, it could take another half an hour.
So worst case scenario it could take you almost three hours or more from when you land until you get to MGM.
Best case scenario is it takes fifteen minutes from landing to getting to the bus. You are the last person on and the bus leaves five minutes after you board. You are the first bus top, and there's no one in line. You are at the BWV and can walk to MGM. In that case, then you could make it if you hustle. But I wouldn't count on it.
Anne