OK, the banner at the top of the board for 3½ years had Macaws. Last month, they disappeared. I understand why they are gone and why they aren't coming back. OTOH, I liked 'em and I miss 'em.
What do I expect?
I don't expect many changes in the next 20 years. I do expect computers to improve. I do expect many of the things others mentioned to be available. I don't expect them to be common. Rebreathers have been around a lot longer than SCUBA. There are reasons they've never become popular, those reasons are not going to magically disappear in the next 20 years. Ultra high pressure? High pressure tanks have been around for almost 20 years, there are syill lots of shops who can't fill 'em. Ultra high is a pipe dream.
Regulators haven't really improved in over 20 years. They won't improve in the next 20. There's nothing left about a regulator to improve. They already breath as easily as if they weren't there. They can already deliver all the air 3 people can use at 100 ft.
Heads up display will be around, but it won't be common. There's no demand for it outside the military.
Communications and full face masks have been around longer than I've been diving, why should they get popular now?
"microbe that will live in your bloodstream and consume all that excess nitrogen, eliminating narcosis and bends forever"
Someone is smoking some powerful weed.
Fluid breathing medium isn't practical.
I expect to see agencies continue to lower standards. I expect it to get to the point where it becomes almost impossible to dive without a baby sitter. There are places it's getting like that now. Now you see OW trips, Advanced trips and tec trips. What we consider OW trips today will be considered too advanced for those holding an AOW card. This might not happen in 20 years, but that's certainly the trend.
What would I like to see?
I'd like to see agencies start to raise standards. I'd like to see dive travel get cheaper. I'd like to see dive babysitters disappear. I'd like to see contact lenses that allow us to dive without a mask. I'd like to see gills. I don't expect any of those, but I'd especially like the last 2.