Were the Pens over the maximum number of contracts?
By my count the Jokinen deal brought the Penguins up to 49 contracts and this drops it to 48 (52/51 overall, but Pouliot, Maatta, & Harrington don't count against the 50 contract limit this season).
That said I do think contract numbers are what drove the deal - Killeen has the least value of any contracted Penguin (currently playing in Orlando...which is not Pittsburgh's ECHL affiliate) and is a free agent at the conclusion of the season...there's no reason for Columbus to trade for him other than clearing a roster spot to sign a college player or two in the next few days. Expect the Penguins to return to favor eventually. We know Jarmo and Ray get along, so I expect there will be plenty of these minor swaps the next few years.