That’s a tough question, because of how fun Splatoon 2 is and how far away Splatoon 3 seems, plus you’d get a lot of practice in before 3 comes out.
However, if I were in your position, I’d wait for 3. Splatoon 2 no longer has regular Splatfests, not even sure if they’ll continue the rematches they’ve been having. The gameplay will fundamentally stay the same, so you’re not really missing out on a unique gameplay experience if you wait for 3. (From what’s been revealed, the gameplay will be even better.) The only thing you’ll be missing out on is the story mode and possibly the pop duo, Pearl and Marina. Oh, and the Octo Expansion, which is also fantastic.
But yeah, kinda late to get into Splatoon 2 now, imo.