I personally would not/do not consider things that way.
I tend to discount future resorts because so many plans have been dropped from the table. Another possibility, though it is an unlikely event, but any resort could be dropped entirely from the system. So I have never bought a contract with a consideration for future any further out than resorts that currently exist. They are very upfront in their agreements that one should not count on future resorts and I have always taken that to heart even though now they highlight future resorts to encourage direct purchases. Again - way too many changes of plans in the past to count on any of that.
Rather, if I got to 2042 and now wanted to stay at whatever future resorts they had opened between now and then
that is when I'd consider buying to stay at them then but I would not in 2019. I might not even like any of them or I might be perfectly happy with what is already here. Now if there was a resort I absolutely loved in any future offerings then I'd reevaluate. Or if I was still happy with most places I still had access to I'd likely I'd rent out my points and pay cash or some other version but I never have thought of sinking money into
DVC promises for future offerings. Nope. No way. What is available in discounts today is much more valuable IMO than a concern of having a dozen options to stay at over two decades from now.
To be upfront other than a resale I just purchased all my points do currently allow me to stay anywhere but I'm going to mostly stay at what currently exists. And I always have a downsizing plan in my head. If I implemented it I'd keep the restricted resale and another small grandfathered contract or two just to have the qualified membership for discounts/perks, since I already have that. No thought at all to not being able to stay at promised future resorts as there would still be SSR, AKV, BLT, VGC, VGF, PVB, CCV and Aulani after 2042. As it stands we mostly rotate thru 3-4 existing WDW and VGC and then pop in a stay at others periodically. Yes, 7 resorts will still be more than enough and DVC resort promises get zero weighting in my consideration.