Here is my take on this:
Martina is entitled to her opinion and her opinion has much more impact than most people's opinion.
I do not agree with her when she talked about Murray though.
Murray does give credits to his opponents but that doesn't mean He accepts when He loses a match, that is his personality. Murray's problems are more technical (forehand, serve, too defensive..) than not giving credits to his opponents.
About Fed I disagree with her. If Fed is able to play his best, like at AO this year, He can still beat anyone whenever they play their best depending on the surface, but she is right when she says that Fed's dominance is over, and it's been over since got the mono before AO in 2008, since then, everything is different.I also agree with her and she says Fed can't get any better, He can be a little better on his backhand, but it will a lot of work, and I am not sure if He will put that work on it.
About Nadal she is dead wrong. Nadal can't get much better, and Nadal doesn't only play Federer, He also has to play others to get to the final, and the field is getting closer and closer to Nadal, not to mention the ones that already beat Nadal lately and some can thrash him on HC. Nadal's major wins this year were a cakewalk in every single one.
He didn't have to play more than 2 top 10 players to win it, and they were not strong mentally. However if no one manage to get there that is not Nadal's problem. He did beat Djokovic when they both played their best, that was probably the hardes major He won this year, but even though Fed would have beaten Nadal if He were in the final.
She is wrong again about Nadal being a number one being healthy. There are many players coming up that will be able to beat him, how can she predict the future?
Del Potro is the one who will take his umber one away from him and del Potro is the one who will be winning 2 majors a year, not Nadal, in fact I think next year will be the last year Nadal will be on the top. I really doubt Nadal will win more than 12 at best.
Another thing is, ATP is not WTA, ATP has a strong top 200, and people are even watching challengers now, and that shows how interesting challenger have become, not to mention the ATP.