As long as you enjoyed them, remember them, and continue to appreciate them, then that character, your hero or heroine, will always exist
It’s friggin crazy that half of these characters are gone in New 52. I can always hope that DC bring them back later :(
Characters come and go in comics. It is part of what we love. Remember that Hal Jordan was essentially gone for over a decade to make room for Kyle Rayner (who is a fan favorite now), and then Geoff Johns brought him back to spectacular effect for his 9 near run on Green Lantern titles. Nightcrawler has been dead for years in X-Men continuity, and we may see a return (I miss him!). As for popular characters who have not been seen yet in the New 52, this means we have an inevitable introduction story to look forward to. Personally I want a good Kalder as Aqualad introduction.