I would probably lean towards the trip, especially since you say that you haven't outgrown your current camera yet.
The price probably won't get much cheaper on the K-7 - but it's not going to get much higher, either - and the camera will be just as good when a new model is released as it is today. It's build very sturdily so even if new ones aren't available, I would have no issues buying a used one. (Heck, my K20D, with over 15,000 shots, is on its way to its new owner in Australia right now... and it still works as good or better than day one.) You'll also find plenty for sale as us lemmings who buy the latest have to sell their "old" cameras.
What you're buying, in a large part, with the K-7 are all the external controls - which are fantastic, but if you're doing OK without them, then that may not be a compelling reason. The screen is much nicer... but again, that doesn't make your pictures better.
The other question is - how would you feel being at Disney solo? If you like solo traveling, then that helps. If you're not sure, then maybe it's not the way to go. It does mean that, if you have photography on your mind, you can bring a tripod and do whatever you like all day at your own pace, even do some ND filter tripod work during the day.