I'm not sure that I would attach the word "investment" to
DVC in any fashion. My contracts will be worth $0.00 at a pre-determined date, and that's not really a status you would associate with an investment.
But that issue aside, I don't particularly think that outside factors have much of an influence on any sort of DVC value. For instance, look at the resale values of SSR and AKV. The ending contract date is only 3 years apart for these two resorts yet there is a $10-15 price difference in what people are getting for their resales. The same holds true for OKW vs BWV / BCV. Despite identical ending dates OKW is getting quite a bit less via resale.
On that basis, I think each resort stands on its own. Adding new destinations (like Hawaii) may broaden the appeal of the entire program, but other factors will play a much greater role in pricing. Since BLT, VGC and even the Treehouse Villas opened--and Hawaii was announced--most resorts have lost value on the resale market. Factors like the ending date of the contract and general state of the economy seem to be having a much greater influence.
As for the theme parks, I doubt that plays much of a role either. For one thing, many people wouldn't name the Magic Kingdom as their favorite park. Also many who like the MK probably don't see a lot of benefit in the Fantasyland upgrades (older children, no kids, etc.)
I'm sure there are some who will gravitate more toward BLT due to the scheduled MK enhancements, but I'm not convince that the numbers are large enough to impact pricing.