So because you play on shared internet Blizzard needs an "idea" for after P500?
Perhaps play on better internet or only play your Hardcore characters when you know others are not using it. Judging by your profile you haven't even attempted Hardcore yet.. I'm sure if you played carefully you'd be fine.
It's not like someone will shout from another room before using youtube. Shared Internet is that, same router, someone downloads a large file, latency goes above 1k (that is, more than 1 second before you realize an elite used vortex, etc, etc.). Besides, I've played HC before (98 in D2, no shared internet back then) and is more like a job, a project, than a game.
Anyways, the question goes towards content in the game. Once all 5 classes reach the highest level available, what's next?