Giggs has no managerial experience, it'd be a massive risk for Man Utd to let him become manager of the 1st team. I don't think Mourinho will be sacked yet any way.
Van Gaal have a lot of managerial experience but he was failed last season and i think experience doesn't really matter for Manchester United but they must find the manager who could to motivate players because their mentally really fall now and in my opinion Manchester United just have not found the right manager because very difficult to find the successor of Ferguson