macOS Big Sur is upgrading the Messages experience quite a bit with the new software.
Pinned conversations, for instance, are coming to macOS Messages app. This will make it easier to keep tabs on a conversation when you need it, and easily jump back into it. The new group conversations are coming to Messages as well, which means you’ll get an updated way to see who is in the conversation, the most recent person to respond, in-line replies, and mentions.
Apple did not specifically mention a switch to a Catalyst app for Messages on macOS Big Sur, however.
The new Messages will have a built-in search function as well, which is one of the most oft-requested features within the app. And if you’re a fan of Memoji, Apple is making it easy to quickly edit your Memoji within the Messages app on your macOS Big Sur device.