2K sent over word to Loot Ninja that they're working on some patches for MLB 2K8 for a few issues. Mainly, the framerate issues are being fixed on the Xbox 360. But that's not the only console with stuttering issues. The PS3 version is about the same in terms of the slowdown in the field.
When asked about a patch to address these issues on the PS3, a representative for 2K had this to say:
"At this time, these are the only updates 2K Sports is working on for MLB 2K8 for these issues."