If you're familiar with kernel releases it seems pretty normal to me. There have been some really major features merged in normal 2.6.x releases. I think they gave up long ago on trying to decide when a feature is cool and/or big enough to constitute a big version bump. It seems likely that they would increment it just to mix things up, not because of features.

Though my personal preference eliminates the dots all together (except for post-facto stable release (e.g. 2.6.39.2)), so the kernel released next would be kernel 3, the kernel released 3 mo later would be 4, and so on.