My feeling is still that if the Phillies continue to see the value of his age, stuff and salary (as well as remaining options if need be) so will opposing teams, if the Phillies do decide to move on.
There are also a lot of other teams who could more easily take their chances with him in leverage, not having the luxury of signing a Keller as the Phillies did (never mind how that worked out).
Honestly, if you pencil in Keller, McFarlane and Bowlan (as well as Duran) for next year, the Phillies don't really even need Kerkering, and need LHPs more. Sure, that gives them the luxury of slotting him lower (or optioning him), but also might make a trade the best use of him as an asset. But if Keller can't pitch or can't pitch well, then, ironically, Kerkering is the best option to replace the guy they brought in to replace him.