SEGA has yet to spill the beans on Sonic Frontiers Definite Edition which was recently rated in Korea. Today, SEGA has added a new description to Sonic Frontiers on Steam and permanently dropped the price of the game on Steam leading many to suspect that SEGA is on the cusp of an announcement.
Sonic Frontiers gets new description and Steam price drop suggesting Definitive Edition coming

I hope they release a free upgrade for switch 2.
It won’t be free.
Crossworlds wasn’t (though it’s not expensive). And, judging by the “Definitive Edition” thing, it’s more likely a separate game that you’ll need to buy again. Otherwise there was no need to drop the price of the current version.
Something tells me that they’ll delist the original soon.
Yes just like Sonic X Shadow Generations.
Crossworlds’ upgrade wasn’t free. This won’t be free either.
Hope it will be an upgrade for 10€ but after Generation X i don’t think so…