Didn't find any official word, but went to a review and video of the treehouse villas made by "Deb" at allears.net. People are allowed to leave comments and ask questions at the end. It's where I found this info, grain of salt and all that...
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DEB: I'll be getting some pics up soon, but all the parking is off street like the spaces you saw for the accessible villas. There seems to be enough space unless all adults in your party have a car there.
COMMENT: With regards to parking, we were told upon check in that we only get one parking spot per treehouse. We did have trouble parking one night and ended up parking in a "non" spot....we made one ourselves!! Several cars parked in the spots dedicated to our villa did not have parking passes. We did call and complain about the parking. Several minutes later, the spots opened up and we moved our car. I think this will become more clear as CM's are more familiar with this resort's specific policies and letting people know that only one car per treehouse is allowed!!
DEB: Thanks. That changed a bit from what we were told opening day. I"m sure the resort is trying to work all the kinks out. Also, parking spaces will vary depending on how many folks don't have a car with them.
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Again, I don't have a solid number of parking spots for the Villas, but I suspect that, unless someone who is staying there invites a bunch of people who aren't staying there to visit, you shouldn't have a problem parking 2 cars. For every group with more than one car, there's probably another group relying wholly on Disney transportation.
FWIW, even though I think the Treehouse Villas look awesome, and I did book a trip there, I did wind up switching to Bay Lake Towers, mainly because of location and transportation issues. Like you, I'm one of those lucky ducks that enjoys SSR, but I do sometimes prefer being closer to a park, especially the proximity to MK that BLT can provide. One of the nice things about staying in SSR is being within walking distance to the shopping and dining of DtD, but staying in the Treehouse Villas, it's not as close as walking distance; with our two kids, it would require using our car or the shuttle bus just to maybe do some window shopping. And even though we always use a car more often than not, it's nice to have the option of a short walk to a bus stop (especially when going to MK) and that is just not an option with the Treehouses. If we were looking to do much more lounging, I think Treehouse would be a much better deal for us, and I do intend to try them when the kids are a little more mobile (currently a 3 year old and an infant), can both get in and out of cars by themselves. There are pros and cons for every DVC resort, heck, there are pros and cons for every resort period. But for us, for now, the isolation of the Treehouses outweigh the coolness of the villas themselves.