If Disney released Muppets Family Christmas on dvd, i have a real good feeling that they'd learn from the TMS S1 dvds and be aware of fans' discontent with the previous MFC video releases and put its full financial and legal might behind them like they did the subsequent seasons of TMS...i'd think Disney would be drooling over themselves to be able to put a dvd out there of the Muppets' most beloved and requested specials with "FOR THE FIRST TIME EVER - COMPLETE AND UNCUT" all over its packaging and advertising.
These days i'm more concerned that with a Disney MFC release, the bigger challenge would be in clearing the rights to the various families of characters than the songs. Most likely, it wouldn't be a problem - Sesame Workshop has always been never provided any problems at any time in the past with allowing Sesame characters making cameos in other Muppet previously filmed productions being allowed to be in the video releases...the Babies are already owned by Disney as well, and i can't see Henson not allowing the Fraggles to appear...the only slight catch would be if they had to get any kind of approval from HIT Entertainment for the video rights - if HIT has any kind of control/approval of Fraggles on dvd releases, they may decide to get revenge on Disney for not allowing Kermit to appear in _their_ Christmas video releases of Emmet Otter and Christmas Toy. But again even in the probably unlikely event HIT had to give its say-so, i think they would either broker a deal where they would allow the Fraggles to appear in MFC, Muppets Celebration of 30 Years, or Muppets Celebrate Jim Henson dvd releases if Disney gives them permission to use Kermit in any subsequent releases of EO, CT, and the like. Of the various companies, Disney is the big corporate shark here - they can throw money at the other companies and get the character and song rights, it's just more in the reverse when HIT wants to use Kermit in a dvd, they can't afford Disney's terms (or after some of the stuff we've learned by now about HIT, they may have just been to cheap/uncaring to go through the trouble)
But since if all goes to already well-laid plans, all three character groups: Muppets, Fraggles, and Sesame Street should all be hot properties all at the same time - and i'd be willing to bet that not only will there be a 2009 or 2010 release of Muppets Family Christmas with all songs intact and (lost footage aside) uncut, but also with awesome special features!