I disagree, because it seems to me that Guardiola's tactics are still as successful as it was during the 2008. Bayern Munich won the bundesliga by a long shot, and although they weren't as great as we thought they were today, Giardiola's tactics are still as effective as ever because it purely focuses on possession and that was evident except for the possible fact that we have players who are just simply bitter than theirs (like Welbeck and Boateng), and that is one way to break Pep's tactics, alongside parking the bus if none of our players arent as individually bettet than any of the bayern players, imo. So no, I disagree that Pep's tactics are falling, because judging by the long term results so far, its working.
Lets face it. It is no longer 2009, when Barca could easily win every game when teams just didn't know what to do without the ball. Teams who played against Barca and lost, began to learn how to cope with this problem. One of my friends once told me, any team will be able to beat Barca in a few years. I didn't believe him but he was right. Pep Guardiolas tactics are amazing and work like a charm against inexperienced teams such as those of Bundesliga. Once, Barcelona played Inter in 2010, whom they had played multiple times that year, they found it way harder to win. Chelsea, similarly, also played against the likes of Barcelona many times, therefore Bayern struggled against Chelsea and found it difficult to win. Therefore, in my opinion nowadays you can keep posession for the entire game, but you still may not win. That is what is amazing about football. It evolves around the success of other teams. Teams learn how to beat teams whatever their strategy, hence the lack of consecutive UCL winners. My point is that, Guardiola must alter his tactics to be successful, he can't play the same game for 6 years. Anyways those are just my thoughts. It will be great confidence for Man United to tie agianst Munich, however, I just don't see them succeeding agianst a well prepared Bayern, and Guardiola at home. Just my 2 cents.