Literally the comment of the new arc stated Luffy will finally take on the WG and that‘s what this arc is about. It isn‘t the Yonkou Saga anymore, guys…
It is an it isn't. In reality it's more like the One Piece saga which will require Luffy to fight 1/2 more Yonko, but that's also leading to major showdown with the WG.
This is why this arc certainly has importance. CP0 likely gets away with the Seraphim eventually (even if Lucci loses here, I can't see the Seraphim not being stolen, it's pointless if they aren't a threat for later after all the setup), but Kuma and Kizaru showing up has significant potential on more Marine/Revo related content.
Whether they are resolved characters after this arc is another question, but Kizaru showing up doesn't spell good news for anyone imo. Kuma is a question mark, and depends on what he's allowed to do. Is he being controlled? Does he have a personality or directive? Is he protecting Bonney? He didn't save her 2 years ago, so it's interesting...