Based on Nvidia's pretty consistent release schedule, the next new architecture release is close to a year and a half off, late q3 to early q4 of 2022.
I wouldn't really call Nvidia's release schedule all that consistent. As far as releases over the last decade go, the 30-series launched around 24 months after the 20-series, which in turn arrived around 28 months after the 10-series, which was 20 months after the 900-series, which was 16 months after the 700-series, which was 14 months after the 600-series, and that came 16 months after the 500-series.
So, Nvidia's release schedule had typically been around 16-months per generation. That did increase in recent years, though that may have been at least partly due to a lack of competition at the high-end. However, now that AMD is once again being more competitive in that range, and there's also the unknown of what Intel will be doing with their graphics cards that could be launching later this year, there's the possibility that we might be seeing a new generation of cards a bit earlier, though probably not until at least next spring. Or at least something along the lines of their SUPER refresh if Intel's hardware proves competitive and they need to adjust prices. Though the current availability situation might disrupt that, at least if the mining market doesn't collapse in the interim.
I wouldn't expect double the performance for the next generation of cards though, but perhaps something like a big boost to RT performance might be feasible.