The appointment, and the timing was done with an eye on Pogba, if you ask me. The United board were afraid of him leaving in January, and he's too valuable a marketing asset to lose. He's become what Rooney was at the time he wanted to leave in 2010. Brand wise, he's their most valuable player by far.
Solskjaer can't fail. The players will improve because Mourinho is gone, and the fans will never turn on him. All he needs to do is keep the players happy, and play more attacking football. League wise, I expect they'll stay pretty much in the same place, around 6th/7th, with 5th a possibility.
Afraid of losing pogba!? No club will touch him with a 10 foot Barge pole for the money the rags want! He is a 50m Squad player.