I know most of the posts here are considering the extension from a financial standpoint, but let me interject a slightly different observation.
In 2042, OKW will be 50 years old.
Have you recently stayed in any hotel or resort that is 50 years old?
We just got back from one built in the early 80's and it was WAY out of date. No central a/c (had window units). Small bedroom. Small bed. No "built-in" microwave. Older appliances. Just tired.
That's a 25 year old resort. Now, imagine what a 50 year old resort might look like...
No a/c. REAL small rooms. Older electric. Out-of-date insulation (sound & weather). No room for newer, in-demand appliances (washer/dryer, dishwasher, microwave, etc). Out-of-date ammenities. Etc, etc, etc.
People's living habits change as technology changes. OKW is only 15 years old. How long have we been told we're getting DVD players? By they time they put them in, THEY'LL be out-of-date (for HD/Blue Ray players). How bad do the A/C units drip from the ceilings in every studio we've stayed in? How bad is the mildew in the bathrooms? What's it going to be like in 15 more years? How about 15 after that? Then, there will STILL be another 5 before the ORIGINAL contracts are up.
Vacation habits are going to change, too. I wouldn't think of staying in a 50 year old resort. Even if they kept up the maintenance (which I'm sure DVC will do). It would have to be COMPLETELY gutted and remodled (which I doubt DVC will be willing or have the funds to do).
50 years ago, you would be lucky to have your own bathroom. 20-30 years ago, you felt like royalty if you had a coffeemaker, free daily paper, and microwave. Now, we wouldn't even think of staying somewhere without A/C or a telephone. Many of us wouldn't stay somewhere without internet access.
In 10-15 years, we vacationers might expect flat-screen HDTV's, TV's in the bathroom, granite countertops, king-size select comfort beds, bidets, computers w/(free) internet access, cappuccino makers, and who knows what technologies that haven't been invented yet.
At that point, we might not be looking at OKW the same way we do now. And, so will people looking to buy into DVC through resale, especially if there is a new DVC resort offering the expected ammenities.
So, I doubt I'll be plucking down $25 or even $15 a point to use a 50 year old resort 35 years from now. I'll invest the money and hope that the inflationary cost of getting into a new DVC resort in 30 years will be roughly the same as I can get investing.