2 years is not remotely enough time to spin up a competitor. It's not even enough time for a current leading competitor to spin up another fab.
If you are a newcomer you are talking a decade or more before mass production. If you are HK Hynix perhaps 5 years or so.
The majors all have large fabs under construction, but the majority of new production from those facilities won't be coming fully on-line until 2028 at the earliest. Even from the date of first wafer shipped most of these facilities take 6-12mo to reach mass production level output.
Chinese DRAM is interesting only because they started building capacity (expertise) a decade ago. Only now are the expected to have any material impact on the total volume of the market. And if they want to gain even more market share, they will be under the same ~5 years to spin up a brand new fabrication plant. Perhaps a bit less because they are China, but still multiple years.