I wonder if we'll see that again. That's a pretty powerful piece of equipment, if you ask me, and it's pretty daring to had it over to a child, even one that appears as mature and intelligent as Hermione. And everything else seems to show up again (which, actually, I like -- I hate when series writers, for books or TV, create something fantastic and then just drop it and forget about it).
I thought the Ministry's entire stock of Time Turners were destroyed in the Battle of the Department of Mysteries in Book 5. I seem to recall Neville or someone blew them up.