ItWasMeantToBe19
Manakete
To make things more clear, there were 3 job listings.
The two first were posted at the same time (October 4th, 2019) and included:
hiring for a 2D action action game in Kyoto. (EPD10).
hiring for a 3D action game in Tokyo. (EPD8).
And the last one was on August 6th 2020 for a level designer for 2D Action Game in Tokyo. (EPD8).
Also worth noting that people like: Takayuki Ikkaku, Yusuke Amano, Shigeyuki Asuke, Ryutaro Kanno have worked on Splatoon 2 and have not worked on Splatoon 3. These 4 names worked in some capacity on previous 2D Mario games (even as Directors) so it seems like their absense in Splatoon 3 makes the new 2D Mario for 2023 a very safe bet.
"A very safe bet that they managed to make what is probably a reboot of one of their most important franchises within four years, half of which was during COVID" is silly to write.
This will take as long as it takes for them to be happy which could take a while.