I raised this point in a blog post, and after some more thought, I'd like to make a concrete proposal on how long we should support LTS 2.0 for.
By necessity, LTS 2 will ship with GHC 7.8 support instead of 7.10. Obviously, many people will be interested in getting onto 7.10 quickly, and I'd like to avoid delaying that. I'd also like to start moving up the support window on each LTS release. My concrete proposal is:
* We move from a 3 month window to a minimum 4 month window
* We keep the option on the table to extend support for an additional two months
* Once Stackage Nightlies are building reliably with 7.10, and we're in that 4-6 month window, we make the move over LTS 3.0 with 7.10 support