I don't think it's really a problem.. Have you seen cases where things have been wrongly deleted? As Shog9 says, there's not much being deleted..
It requires 8 votes to delete something (close votes + delete votes), and it can just as easily be restored.. >3k users can dispute the closing of a question (and by extension, the deletion) by voting to reopen it, as can everyone else can via comments..
There may be more users with 10k rep, but anyone who has spent the time to get to 1000 upvotes on their content (ignoring the daily-rep-cap, down-votes, community wiki etc) is probably fairly.. invested in the site. It takes just as much effort to get to 10k rep now as it was when there was no >10k users - I don't see why new "10kians" should be any less trustworthy..