I think one of Casualty or Holby City will sadly be cancelled next year. I get the feeling that the BBC seems to have lost faith in the Holby franchise recently. If I had to say which, I'd hope it isn't Casualty, it's in great shape at the moment.
As for any other continuing dramas...it's the obvious one. If Hollyoaks' ratings don't rise before the new year, I can't see Channel 4 sticking by it. I reckon they may move it to E4 after a while, it's still reasonably rated over there.