His body type is not conjecture, even his biggest fans could not argue he is a natural athlete, and SAF has come out and publically stated Rooney is prone to weight gain, this is only going to increase with age, that is undeniable, and given both past history, SAFs own comments about his training issues and the evidence of our own eyes it is not too far of a stretch to suggest that he is far closer to the end of his top flight career than the beginning.
If you take the body/form/fitness issues as read then why would you want to offer an extension, I would bet my left nut that he wouldn't take a pay cut, It is difficult to justify a salary as high as even the lowest figures quoted for a player who is going to become less and less influential.
What knowledge do I have of his disrespect, lets see, being so arrogant that he cant see that he is playing so badly there are others who deserve to start more than he does just for starters