SoCal resident here, I think VGC will come down to VDH prices once there's a significant resale market. Quick math shows that VDH at $180/point would be equivalent to about $240/point VGC. Looks like VDH isn't moving much at $180 so the resale market will likely move lower as it matures. Comparing the cheapest VDH contract at $152 and VGC at $240 (looks like it sold recently), gives you a price per point of $14.83 for VDH and $15.41 for VGC. Seems similar; however, VDH has cheaper studios that cost about $148 for the duo and $193 for the deluxe. VGC would cost about $261.97. These would be for the cheapest time of year. During the holidays VDH still comes in at $460 for the deluxe vs $570 at the Grand. I believe the bedrooms were cheaper too, but didn't bother comparing as I'm not too interested in them at the moment. Maybe when my kids are much older. Point being that VDH does offer a pretty good value even though many think its worthless on resale.
Looking at other places on this forum, and I think $150 per point will likely be a realistic point for VDH resale contracts. That likely puts the floor for VGC at about $220.
The curveball will be
Disneyland forwards effect on VDH. I think it's possible that it will become even more desirable over the grand once it abuts Disneyland. If this does happen, the next 5 years will likely be the cheapest you will ever see VGC. VDH will probably not drag down the price as much.
I don't think a third
DVC property will happen until a third gate happens. I also think Disney will kill for a third gate as that would make Disneyland finally worthy of a full week stay for most people. Turning toy story lot into Disney springs without a 3rd gate seems pointless. I feel like the reason it works so well in Florida is due to visitors being there for at least a week, but Disney does like doing cheap and stupid decisions like they aren't one of the most powerful entities on the planet. Maybe they will prove me wrong.
In short, get VGC before they expand the parks because after that I think they only become more desirable and more expensive.