It will be a mistake to try and keep Kanter. Im assuming Dennis Lindsey is smarter than this and is just saying what he needs to.
Kanter can see what's coming on this team. How can he not? Rudy is obviously emerging and Favors isn't going anywhere. Why would Kanter think that he has a shot to be the starter on this team for years to come? He has to believe that nothing is going to change. Any kind of boost in minutes will be temporary.
From the Jazz perspective, they should not be thinking anything other than Favors and Rudy are the future. All parties know what's going on here.
If the Jazz don't trade Kanter before the trade deadline, then I predict Kanter takes his qualifying offer next year and gambles on getting a bigger contract the next year when the cap increases dramatically. It's possible that Kanter gets a nice offer he is happy with this summer, and maybe we could do a sign and trade, but I think that's unlikely.
Once he signs that qualifying offer, we have very little leverage. Teams aren't going to give up much for an unrestricted free agent. Then we are stuck with a disgruntled player we have no use for and is going to screw with team chemistry. Then all we are left with is a little hope he would sign for very little and be willing to come off the bench. Not likely that's happening.