O.K, so I have been a member of chess.com for well over a year and I have reached the magic level of 2000+.  This was done through hard work on openings and some tractics training, as well as developing some positional grasp.

However, I have seen people improve from around 1700 to 2300 and even 2600 within the same period of time. It is supposed to get harder the higher you climb, so what is the secret? Can some of these elite players share with us?

First, I'll assume your referring to ONLINE ratings as opposed to LIVE. That said, those ratings are about 300+ points inflated at most levels in my estimation. So, we're now talking about someone improving from about 1400 ELO to about 2300 ELO in a single year.

My opinion (if the 1400 ELO represented true initial skill): extremely unlikely, but not impossible. Just my view, for what it's worth.

Given that everyone comes in at 1200 regardless of actually playing strength, any strong player's rating will exhibit a rapid increase, however.

I'd add this: To add 600 points in a year is quite a challenge for anyone, but certainly feasible as tested in real-world, certified otb play. Take the case of a genuine beginner who enters his first otb tournament, somewhat prepared but a true beginner, and gets a rating of 1200. One year later, after smart and hard work, he is a 1600. He might even make 1800--that's your 600 points in a year--and he would not have to be very talented to manage this.

More than that and I'd say our player has significantly more talent than the average bear (or has a very good teacher).

For an established player this would be much more difficult, though Fischer managed >500 points in a year starting in the 1700s, and then less than a year later he was US champion-well that's Fischer and there aren't many like him.

edit: when I say "true beginner" I mean a serious beginner, one has has played chess informally, perhaps a lot of it, perhaps even with so-called tournament players, not a beginner in the sense of knowing how the pieces move and a few more rudiments.

maybe a handful of people go from 1700 to 2100 in one year. If you peruse all the young American players- hikaru, robson, hess, etc. you dont see that big of a jump. IM Shankland might have done it I recall playing him when he was rated 1850 and the next supplement he was 2050ish...

2600 from a steady 1700 in one year sounds like cheating to me.

I read an interesting article on turn based chess being much less accurate a predictor of skill as live chess. I would assume this understanding would transfer over to the improvement curve as well.

if i tell ya, youd be as smart as me, an my friends, so il give u a clue,more games and work harder!!! cuz there not alot wrong with your game!!! 

Probably cheating involved.

 The hardest kind.