Gonna say it right now:
Restricting old content when new content comes is a bad idea.
People want more to do and more options, not less.
I'll want new rewards but I still have achievements and a few shards left to get from Hoth.
Hoth doesn't take much effort for established players: just let them both be run, or make parts of Hoth simmable for those who achieve a certain level for long enough.
Heroic Pit didn't go away when AAT or Sith raids came out and people were fine with that.
I genuinely don't understand how some of these decisions are reached.