Nothing lasts forever but let me ask you: What would the domain substitute be? There likely could be one but there is no chance in hell that ICANN, the registries, or investors would EVER let the domain become extinct or irrelevant. Things end, true but there are things that ride the wave until the very end. It's an unrealistic belief that the domain will become extinct beforte the Internet does. And like TV and radio (and porn despite its critics and the fur/leather industry despite PETA), the net has no signs of ever becoming obsolete and/or a relic. So yeah, the net might die one day but it's as perennial as the other things I've mentioned. And it'll likely never cease to exist at least for a LOOOOOOOOOOOOOOOOONG time. Chances are, you great great great great grandkids will know what a domain is, even if they access it differently.