The current reward pool is about $6,000-7,000 per day, so the most that a single post could make (if all other posts got $0) would be around $6-7k.
The price of STEEM would need to go up in order for the reward pool to go up to the point that $15,000 rewards for a single post to be possible again. If the price went up to around $1.00 per STEEM coin, then the reward pool would be closer to $60,000-70,000. Then a $15,000 post would definitely be possible.
I think the record was somewhere around $43,000 :)
After HF 17, posts are paid out on a weekly basis and reward pool will contain on average $50,000 and payout an average of $6-7K per day. An extremely popular post (relative to everything else) could still pull in $15K even at today's valuation.
Overall HF17 should smooth the rewards and prevent large posts from dramatically impacting the average payout-per-vote of other posts.
Cool, thanks Dan!
Nice, can't wait for the 7 day rollout :)