Every player has a price and for a big fee I would have no problems with selling Henry. Having said that I think this year should not be held against him. Thierry has been absolutely brilliant for Arsenal and I think he still has lots of great football in him.
Vieira was a different case. For three straight summers we had to put up with the "will he-wont he?" stuff with Real Madrid. In the end Wenger got a good price and decided to completely rebuild the side. In some respects we have missed him, but seeing Fabregas, Denilson and Diaby coming through makes me think that Wenger did absolutely the right thing.
I have followed Arsenal too long to expect a trophy every season. As a Liverpool you will know exactly what I mean by that. Sometimes things just dont work out. The only thing you can do is shrug and hope the future looks good. For Arsenal it certainly does.