It's not that hard to get to 1000+ slowly. All you have to do is hang around for years and make the occasional decent comment. If anything this is biased towards old timers.
It's not currently that hard to get to 1000+ slowly. By slowing down commenting and making it harder to even get comments through, this is presumably going to make it harder.
I browser HN daily, been around for coming up on a year, and I'm not even half way there.
Since commenting is such a huge aspect of these sites for me, I'll probably frequent HN much less often since I won't be able to participate in conversation. PARTICULARLY, I won't be able to get in the early comments that are necessary for making high-karma. You can't have your comment show up an hour or so later after "approval," you'll only net a handful of upvotes, because you'll be buried under the high-scoring top comments by senior HN users.
Perhaps make a mid tier, say 500 karma, where you can't endorse users, but don't need endorsement?
I've been around for 250 days or so and am not even halfway there.
Then again, I only say something whenever I feel I have something to add, rather than just blasting comments and hoping to get upvotes (and now, endorsements)