It is kinda tricky. I basically want to ask if someone who was once so into the game of poker, turned into a social player, would he stay the same skill wise or lose more due to poker changing.
In essence, the game doesn't change. It's the people/player who does.
I don't think that Player B would necessarily lose. Maybe he has an advantage over a certain type of player when he plays, if he's lucky to be playing against that player. But on the times he doesn't due to work commitments, he may not have a profitable session.
Player A on the other hand dedicates more time because it's his profession and thus sees and plays against a variety of players, some of whom he can easily peg and identify and then skew his playing style to counter theirs.
I guess Player B can expect to profit, just not in the leaps and bounds like how Player A would because of each individual's time and dedication to the game.
But I could be wrong and there might be a player B out there who's doing a pretty awesome job raking in high profits like player A even as he (player B) holds a full-time job.