The Payjoin project just posted their vision and roadmap including multiparty batch transactions in v3, an ambitious project Spiral's Yuval Kogman has been working on.

Spiral grantee nostr:nprofile1qyt8wumn8ghj7ct5d3shxtnwdaehgu3wd3skueqpz4mhxue69uhk2er9dchxummnw3ezumrpdejqqgpxtqmzcvfha25qr7hyqjlrdl7gpct2v8zr4zg68gzxhmztwtjf3gh76kkx has been super focused and making tremendous progress on Payjoin for several years now. He's been able to attract many other developers to the project, including merging Yuval's project into Payjoin, which is a fantastic outcome.

I find Payjoin to be one of the most pragmatic and promising privacy improvements for bitcoin. We're going to see strong adoption of it in the coming years.