Let's start by what I missing the most, and it's very down to earth: a Lightning mobile testnet wallet!! There used to be Eclair but it's deprecated. And SBW testnet was great, but it's no longer available for download. I would find it very useful for testnet.lnmarkets.com. Also, I tried to teach Lightning to students, but wihtout this Testnet wallet it's more complex to make them feel lightning.. Regarding Bitcoin developments, I'm looking forward to more use cases around Taproot and Taro is a perfect example of that! With stablecoins on Lightning, we could list our products in USD. We could also tokenize new types of assets and trade them at lightning speed, and many use cases we can't imagine yet. Of course, this will take some time, but it's exciting times ahead!