Arcologies or greenhouse super domes for food production of any kind wherever it's desired

Or carbon nanotube mass production so we can build mile-high connected super structures

• Space tether.
• Nuclear fusion.
• Home assistant robots

Being able to photosynthesize. It wouldn't be that hard either, we already can, just not to make food.

Replicator. But that kinda seems impossible so that Black and Decker rehydrator thingy from Back to the Future II.

genetically engineered housing

Universal translator

Matter transporters for work and holodecks for play.

A better battery would be nice.

I would stay in relatively achievable things like a sugar fuel cell or microbial food production. Things we don't quite have yet but not do to the knowledge not being there.