As someone reading everything can about the THV in anticiaption of booking one come February - I knew I read that answer somewhere.
The article in the latest DVC files hinted to the ramps in stead of stairs sometimes. In addition, the dvcnews website said this:
"Despite their rustic name and appearance, the Treehouse Villas will feature state-of-the art fiber optic connections for telephone, Internet and cable TV service. Four of the Treehouse Villas will be handicapped-accessible using a ramp system rather than stairways."
I found that the dvcnews dot com website to have the most info regarding rumors and facts about the treehouses, in addition to photos.