The fact is - more DVC in California would be in much demand. From what I have heard - there are three reasons that DVC has not expanded in California:
1) #thanksAulani - Aulani has not sold well. It is a little over half sold after like 5 years. They are estimated that they are going to take another 3-4 years to sell out. The feeling within DVC is that another DLR DVC resort would dilute the property even further.
2) Part of the motivation for DVC at Disney right now is to replace underwhelming deluxe hotel occupancy with DVC. California doesn't have the same lagging hotel occupancy issues that plague Florida - and have higher room prices. This is one reason that the recent Disneyland hotel refurb didn't result in any room converting to DVC.
3) Space - there just isn't that much space out in California. This new hotel is the first in a long time.
All that said - there is clearly more demand than supply at the VGC - but understand there are only like 48 rooms (maximum 71 rooms if you split up the lockoffs) at the VGC. This is compared to some 3000+ rooms in Florida, and 500+ rooms in Aulani. Because of that - there will EVENTUALLY be a DVC in California. And it IS possible that it could be part of this new resort, the good news is if this new hotel were to have a DVC wing - Aulani should be sold out by the time it opens.