You'll be able to transfer your save data from Splatoon 2 into Splatoon 3 for a variety of in-game rewards, including an early boost to your ranking.
If you transfer your save data from Splatoon 2, you will get three Gold Sheldon Licenses which can be exchanged for Splatoon 3 weapons , "regardless of player level." Also, if you start Splatoon 3 fresh, you'll have to reach level 10 before jumping into the ranked Anarchy Battle mode. With a Splatoon 2 transfer, you'll immediately get access to Anarchy Battles.
You'll also come into Splatoon 3 "with a higher rank, depending on your rank in Splatoon 2." Nintendo doesn't fully explain how directly that rank will transfer - we don't know if, say, S+5 players will still be S+5 coming into the new game - but it does mean experienced players won't have to start from the very bottom all over again. Your matchmaking stats outside of the ranked mode will also carry over.
All this info comes from a new blog post on the official site, which provides a selection of additional information that didn't make it into today's 30-minute gameplay presentation. It's been a blowout of Splatoon 3 info today, as we learned of "large-scale paid DLC", a new 1v1 card game, and a selection of new amiibo. But most importantly of all, we've now met Big Man.
Splatoon 3 is set to launch on September 9, but you'll be able to get in early with a special Splatfest set to run on August 27.
There are plenty more upcoming Switch games to look forward to this year.