VDH is still 6+ months away from opening. VGF resumed sales 3.5 months before the Big Pine Key rooms opened.They aren’t even selling points yet for the new Disneyland DVC. They are letting you very soon rent rooms for cash. They haven’t even announced when they will start selling points and that is a complete different market then WDW, so those sales will not really impact WDW DVC sales.
Keep in mind there are timeshare laws and licensing restrictions which pose issues with these projects. There are also internal considerations, like the fiscal quarter in which Disney wants to start booking the income. (Q3 begins around April 1.)
It is an absolute certainty that they will begin selling a few months before VDH opens, and a certainty that there will be members staying there on points the day it opens. And the same will be true of Poly.