Personally I love the 90 minuet opening legs of Season 4 and 10. Enough time to get to the names and faces of the teams (especially for the general public who haven't got them down months before it airs) and enough time to showcase teams doing real tasks. Even on first legs I have liked, I feel we miss a ton, and sometimes with the two hour single episodes it seems like a little to much filler. For CBS its a win win, and expanding the footage for 90 minutes cost them a small fraction more (primarily due to more editing) and reaps them a 50% increase in revenue. And since TAR isn't really syndicated (not really) they don't have to worry about the difficulty in selling it for an off network run.
But based off of this it looks like an 11 episode season (of course they could always air two episodes over one night).