Hard to say, while they clearly both have huge amounts of knowledge to pass on not sure if either of them have the temperament and patience to be a trainer. Being able to teach is a skill in itself that has to be learned. Mayweather likes to be the centre of attention and Hopkins still has a chip on his shoulder which could hinder both of them as trainers.
As he gets older I can see Floyd following in his father and uncles foot steps and training fighters. He may become one of the greatest trainers who ever lived. I can see BHOP training also, but I think we will see Hopkins with a good promotion company.
B-Hop definitely, he already tries to train opponents just after he beats them, before he beats them he likes to give out critiques and he considers himself a student of the game. Floyd almost certainly not, he doesn't have the patience, intellect and he is too self-absorbed. Plus he doesn't know how to communicate with people, as he admits himself he only hangs around females (who are only there to giggle at whatever he says and take his money).
No don't think so, both would probably go down the promoter type route and I don't think training would suit them. Hopkins maybe at a push but not Mayweather.
Usually great fighters have a tough time being trainers because they don't have the right personality for it. They don't understand why other fighters aren't as dedicated as them, and why they can't pick things up as quickly. How many great trainers were actually great pro fighters? This also applies to other sports.
That's true, the best coaches are ones who didn't achieve their dreams, but their aspirations still remain and are transferred to their pupil.