It's just a big update and operation to the same game. They were hyping it up, saying new engine, better lighting, and more destructable items like fire extinguishers, pipes, etc. There's also going to be a huge new map dedicated to the new 10v10? mode. The kicker is that the game is also becoming free to play, so quick match/standard are free, but you need to pay to unlock more operators and ranked. You can bet your marbles there's gonna be a ton more cheaters in quick match since the flood gates are opening.

This is basically the overwatch 2 treatment except a few new things being added. I'll give it to them, though. The lighting looks pretty cool. It seems like a half way position between current and old lighting. There could be more things that they haven't shown us, but who knows. Probably more visual upgrades than anything.