Checking Tyche's chart, April and May saw huge increases in private sims compared to typical changes, with 176 in the week of April 19, 192 in the week of April 26, a huge growth of 352 on the week of May 3, and 268 on the week of May 17. But this period also saw the greatest drop, a decline of 179 on the week of May 10. These huge numbers were likely why Linden Lab made their announcement saying they couldn't guarantee a new sim for everyone. From the week of November 15 to the week of December 6, there was another period of growth averaging 80 a week. This followed the Lab's announcement that they had more sims available for sale, though still in limited numbers. But in late December, the Lab put further purchases of private sims on hold, at least for now, due to maintenance of it's land store. So the number of sims dropped in the last week.
So what will happen in 2021? Presumably once the bugs are worked out with Linden Lab's move to Amazon Cloud servers and anyone can get a private sim when they want, their numbers will continue to grow. But if glitches cause them to keep new land purchases limited, the increase will be small.
Source: Tyche Shepherd
Hat tip: Daniel Voyager