If we observe the number of users who have joined the new forum during its entire existence since October 19, it is easy to see that the number of users of the New Forum is growing on average by 190 users daily.
Use the link to check it:
https://community.postcrossing.com/u?period=all
Of course, the dynamics of users growth will change over time.
Guess how many the forum users will be on December 31, 2020.
The update of the value indicated by the link that I have provided occurs once a day in the interval of 16:00…17:00 hours.
I think that your link shows the actual value at the moment. But that’s just my guess.
@SkyHound, my Magic Crystal Ball tells me that we’ll have ~6300 New Forum users on 31 of December 2020.
It is about +82% more than now (3470).
Maybe Stefan (@Stevyy ) would also join us? 
Last time I checked, new forum has 3518 users, that’s less than 0.5% of the entire PC users base (801213). Heck, that’s barely above 10% of the legacy forum users (31784).
The new forum is only two weeks old. It’s still too early to call. And given the ease of Single Sign-On (SSO) and the need of transition from old forum, I would expecting more people to join, and trust me, they will join fast.
If I were to give an (educated) guess, I would say around 10K by New Year. Who knows, maybe we will see a surge once they announce the new forum in a blogpost or tweet and somehow everyone joined.
Time series forecasting is the subject of my serious scientific interest.
It would be interesting to come up with a generalized criterion for assessing the quality of the predictions of each player from the group, taking into account the accuracy and distance of their attempts. And, of course, considering that anyone can make as many attempts as they want.
This is not a trivial task. Here, the highest rate depends on the accuracy from a greater distance with the least number of attempts.
Anyone who hits more accurately from a greater distance with fewer attempts should get the highest rate on this criterion.
I will not say that I only think about this, but every time we have a fever for the next million postcards, I wonder how to evaluate the predictive attempts of one or another forum user
I guess we’ll have about 6800 on 31 of December.
Anyway, I think not more than 7000.
But yesterday definitely brought in more followers than expected (+75 accounts more).
The growth of the audience of subscribers to the New Forum is significantly influenced by various fresh internal news events, such as 59 million postcards, some discussible or debatable topics.
I’m a little bit pleased that this prediction was proven wrong, as we’re now over 7200 members here… though admittedly, we sort of pushed the numbers up by writing a post about the forum on the blog.
Maybe time for a new guess for the end of the year?
You are right. It looks like 10860 or about it on 31 of December.
My Magic Crystal Ball noticed that the bounces followed shortly after those dates:
14-15 of November.
Your post in blog was published on 14 of November.
So your idea of the correlation between blog posts and Postcrossing activity looks plausible.
And this is very good, it is so obvious that the blog has an influence to Postcrossing.
Challenge accepted! 
On the last day of last year, the number of users of the new forum was about ~ 11,600 registrations. This is higher than I thought. Which is certainly very good.
January 20 is the last day of the old forum. After that date, the old forum will be read-only.
Oddly enough, but some users continue to write something on the old forum.
I foresee a spike in user registrations on the new forum around January 20th. And this is a good date, since around January 24-26 we will pass the line of 60 million cards. And maybe with new registrations we will get an additional audience for my favorite countdown thread
Nah, I don’t think this happened. 
Those who wanted to move here had already moved by now. The old forum is read-only now, but there were only a few new posts there recently, mostly from RR hosts who hadn’t completely moved their games to the new forum yet. Overall, people seem to enjoy using this forum, and we’re seeing higher daily activity levels than on the old one. Hurray!
At the moment we have about 24800 users of the community.
https://community.postcrossing.com/u?period=all
I will assume that we will reach the 30 thousand level around November 08, 2021.
And by the end of 2021, the total number of users will be about 32 thousand.
And at present about 45 community users are registered daily.
As of yesterday we had we had 33037 users of the community.
https://community.postcrossing.com/u?period=all
New user registrations are slightly (+6…8%) ahead of my summer estimates.
