Communities could be a powerful feature I'd be curious to see how it works in action a bit and how it will be implemented / open source so other applications can tap into it.

Anyone can, communities is powered by hivemind which is an open source software.

Outside of that are there plans for more front end things such as a NFT marketplace

Our work is about building frameworks/infrastructure so that others can come in, it's more of a "we'll give you the tools to build it"

As for NFTs, there's already a few projects, most notable is https://nftshowroom.com/