Cop-out answer, but I hope all of them will eventually succeed here. I strongly believe open source projects are the future.

Lemmy has an incredibly solid base to build from, and with the directions many other platforms are headed, it's likely to continue growing.

For me personally, I'd love to see more out-there communities form, like r/2panelgarfield. I love the experience of discovering an awesome community for something you never knew existed.