I've heard rumors that they've considered spending a season or two in years that overlap with the beginning of Breaking Bad. That's probably unlikely, and it could get really gimmicky really fast.

It seems like the most likely scenario is, like you said, that Jimmy will go full sheister, soon, and they'll spend all of this season and the next setting up for when Walt and Jesse grab him and he thinks it's Nacho. BB only had five seasons; I assume they're planning on the same number for BCS.

I'm still hoping they spend some time (maybe even a whole season!) on Gene Takovic's life in Omaha. These expanding black-and-white scenes where he's trying to keep his head low (and looks like he wants to explode back into Saul Goodman) are really drawing me in.