DVC has about 3 million points left to sell in Riviera and 800k in Grand Floridian. If we assume Poly is around 4 million, that's 7.8 million total.
If we further assume that DVC wants to average around 150,000 points per month, those 3 resorts would take about 4 years to sell out. If sales average 125,000 per month, it's more like 5 years.
VDH could have a negative impact on WDW resort sales. But they've been competing with Aulani for years and the numbers are what they are. Markets are so different that it may not matter much. However, if sales are strong at VDH, it could allow DVC to avoid any deep discounting of the WDW locations. They just have to meet financial goals.
On the flip side, Poly will sell strongly out of the gate which will raise that average.
What really matters: lead time on a new DVC development is about 2.5 years*. If the next resort is new construction, we could hear something before the end of 2024. Depends on how forthright Disney chooses to be. (They've been pretty transparent on most projects in the last 10 years, outright announcing them as work was set to begin.) With a late-2024 announcement it opens in mid 2027. 4-4.5 years from now.
*There were rumors about Riviera as far back as September 2016, which proved to be accurate. It was announced in July 2017 and opened in December 2019. (3+ years from start of rumors, 2.5 years from official announcement.) Poly2 was announced March 2022 and will open in late 2024. (2.5 years)
If the next project is a straight hotel room conversion, they could flip a resort in as little as 6 months. It could be 2026 or later before they have to announce anything new.