Tools (a lot of tools) that facilitate adoption. Lots of improvements and advancements in user-experience and convenience to use bitcoin and LN everywhere.
Basically, things that make bitcoin the best choice for what it was initially meant to do.
I had this idea some time ago, but don't trust myself to build a wallet secure enough to run on Windows (where a lot of VR happens). Honestly surprised Zebedee hasn't done something like this yet
Something that could be easily (and cheaply) used for OFFLINE Bitcoin Payment. Two devices that could do a transaction via Bluetooth (or NFC) and as soon as it gets to some sort of an online-node it could update the chain... Not sure if it's possible.
Also it needs to be very cheap to be used specially on poor countries. That's where Bitcoin has an easier chance for a fast growth rates.
Don't know if it is in the works or not, but some sort of integration with AI, so you could pay with lightning for the use of ChatGPT and the likes. Also, if AI it self could have a wallet so it could spend BTC and do things on your behalf.