I think you're right Kaboul will retire. That's been rumored for about a month now pretty heavily on SC. I'd be okay with keeping Dawson to preserve/divert funds elsewhere, as long as we a) reacquired Caulker or b) made another top quality addition. We could do worse than Dawson as a fourth choice CB, and I think he'd be humble and loyal enough to accept it at his age and use it to push the other three.
Surely he'll battle on though. He's only 28 and Jenas/Dyer have been pretty bad for injuries and kept battling on into their 30's