So I'm quoting my own post since I'm kinda confused, but also interested, as there may be a theory based of this
THEORY TIME!
So I believe that Sonic 3 (the Original) came out in February, and & Knuckles expansion came out some time in October
So I'm kinda confused why they did Sonic 3 anniversary now, and why they didn't do it earlier. I actually believe this is the only time where they did something off date, and unlike the Sonic 1 post, this seems to be intentional
I could see this being based of the Sonic 3 & Knuckles version since that's considered the complete game. If that's the case, that would mean this should have been celebrated in October, not much earlier in May
So the Interesting Implication, and where this theory takes us, is that we could maybe use this to figure out when BOTH of the last 2 fighters will release. The fact they are doing the Sonic 3 & Knuckles posts now might suggest these anniversary posts won't last till October.
These anniversary posts I believe started sometime in July 26th of 2020, So I will say the anniversary posts will at least continue till July.
October is kind of a far off date, as I'd expect people believe CP11 would at the most be released in Septemeber or earlier. However this could just be the start. If we see more off date anniversary posts for games that might be in September, that could be used to take off that month as a potential release date of the character.
In terms of the Sonic Anniversary posts, With Sonic 3 out of the way, we have Sonic 1, Sonic Adventure 2, and Sonic Lost world that will need posts perhaps, though they might just ignore Lost world.