There will always be porn. When they say hooking is the second oldest profession, that's because porn is the first one.
20 years way too far to tell. It probably won't be "the net" at all.
Eh, I'll go for the obvious SciFi answer and say people logon from home and are virtual holograms in holorooms having the ability to experience in all five senses real holosex.
Just make sure you wear your holoTrojan otherwise you'll get a real trojan.

h34r: