Why do your points not really matter?

- twitter already has a huge community -> check

- twitter is known to normal people -> check

- integrated into traditional media -> check

- there are no alternatives with a comparable amount of members -> check

- All of your points don't matter for normal users -> check

What competitors are there to twitter?

- App.net: Probably too expensive for the majority to todays twitter users

- Google+: No good clients, too hard user discovery (no way to find users via convenient handles), real-name focussed.

- Facebook: Privacy Nightmare, real-name focussed, insisting on a limited amount of mutual friendships instead of breadcasting

- identi.ca/status.net: Would be perfect, but nobody seem to be using it

Considering all this, I would assume twitter is going to stay.