I wish they would get rid of 13. But even if she did leave House's team (I don't think she would die of Huntington's now, for reasons the others have mentioned) I don't think that would signal the end of the show. She's not that important.
Reasons I'm unhappy that Amber was killed off:
1) I like Amber (refusing to use the past tense).
2) I much prefer her to House's new team, particularly 13. Taub is okay and I can handle Kutner but mostly because I like Kal Penn, the actor who plays him - his character is a bit of a cipher and I don't think he adds anything to the show. If I couldn't have Amber on House's team, I still liked having her around in some other capacity.
3) It was nice to have Wilson happy for once, particularly after all his failed marriages.
4) I liked the prickly relationship Amber and House had (fighting over access to House etc).
5) Even though her death was clearly an accident (and they took great pains to show that there was nothing House could have done to save her), it still will irrevocably change the House-Wilson relationship. House will blame himself and Wilson will blame him, too. I don't want endless awkward scenes between the two, or Wilson avoiding House.
I'm still hoping it's some sort of hallucination/dream sequence.