Nothing wrong with that, Del Potro showed he can play better than Federer on HARD COURT.
Yeah, that's why he has 1 slam while federer has 9 HC slams (USO and AO).
As for the thread question, i don't think delpo will beat fed this year. The Olympic defeat was probably the last straw and it has to affect him quiet a bit.
A wise man once told me,
don't argue with a fool
'cause people from a distance can't tell who is who.