More precisely, Xabi Alonso is currently being targeted by many of Europe's top teams because of Xabi Alonso's success in creating or building the Leverkusen team as it is today. I think it is quite worthy because Xabi Alonso has shown his qualities so it's only natural that many top teams want him.
I think the rumors for Bayern are still quite far away because so far Tauchel has been successful and has made Bayern Munich's performance quite strong, but we don't know at the end of the season what could happen if Tauchel has failed to meet the expectations or targets that have been set by Bayern management.
If Xabi can win either Bundesliga or Europa League, it's better for Manchester United to hire him and kick the bald guy. Manchester United already lose their legacy as one of toughest team in Premier League. They need to find a good coach who can able to develop the whole team, just like Xabi who wasn't sign many players, but he develop the existing players with a new strategy.