With the Red Sox already owing 80% of NESN, I could see an all-Sox channel in the future, with NESN splitting into two networks: One being 24/7/365 Boston Red Sox (including live game coverage), and the other being the current NESN (Boston Bruins, Boston College, Pawsox, "Sportsdesk"), but without the Red Sox.
I think that were this to occur, cable operators would pay the same per-subscriber-per-month fees for both networks that they now pay for NESN alone (which I think may be a distinct possibility) and place both networks on "expanded basic" tiers.
Such a move would likely result in not just the 120 or so regular-season Red Sox games now on NESN, but also the 30 or so regular-season Sox games now seen on over-the-air TV in Boston (on WSBK-38) moving to the Sox channel (these 30 or so games are already shown on NESN in other parts of New England).
Interestingly, I believe the WSBK/Sox contract has expired. A few years ago, after a long-term contract with WSBK expired, the Bruins moved all of their games (other than those on national TV) to NESN. The Sox will probably follow suit, maybe as soon as 2006.
My guess: NESN will indeed split into two networks: an all-Sox network (including 150 or so regular-season games a year) and an "everything else" network which would retain the NESN name.