My guess is the hope is there that Murphy does something while up, making him a tradable asset. Ryan Murphy is ok for the 3rd pairing, but is not a real replacement for Dumba. I still think that Belpedio would have been a better choice to bring up.
I understand the reasoning behind Murphy over Belpedio though. One of the things that Fenton is here to change is how the Wild get players. Fenton wants what they have in Nashville...where a lot of their players are developed in the minors first. Since they probably don't have Murphy in mind for the future, using him now and letting Belpedio develop more in Iowa is right in line with the philosophy that Fenton is trying to install here. Doesn't mean I have to like it right now.