Vegito was hinted at. If you remember, they dropped the F2P Majin Vegeta who had no relation to any of the new units. Then they dropped Vegito a week after. Maybe this time they decided not to drop a new F2P character and the return of F2P Cell is just the hint, or maybe it's not. Who knows with them, like you said

legends has shown that they will drop units without hinting them first

We'll just have to wait and see if it was indeed a hint or simply an event that returns for the fuck of it. I've seen people argue that since Hybrids is already the top team, there is no way they'd release an Ultra SSJ2 Gohan and to those people I say: Since when do the devs care about balance?