Not quite sure "fed up" is quite right. He said "abused" and that's a different thing.
I think you have to understand Cavendish a little here. I get the impression he wants a great deal of re-assurance, needs to be loved. I also think he tends to have a very self-centred view of things, and often speaks before he's got a full picture. He's probably miffed that HTC aren't gushing over him, offering love and attention and great things for the rest of all time. When the truth is that they have every intention of offering another contract it's just that other things need to be done first to do that.
Besides, there are bigger things than him. For all we know, HTC are sorting out next year's sponsorship without which nobody will be offered a new contract!