I think it's wise to wait until the end of the season to make the call. Certainly would be pretty silly to offer him a contract now when he's clearly not going elsewhere for the moment. Assess at the end of the season and make a decision in my opinion.
Also just to give balance to that managerial record, the last norwegian trophy win was in 2013, the ManU reserves trophies were all 2008 - 2010, and he's since failed with Cardiff in the Premier League/Championship, and been sacked. So he's done some good, but he's also had setbacks, and hasn't won a trophy for 6 years. It might be that the ManU job is the perfect fit for him, but surely give it more time first.