I've seen several players jump 500, 600, 700 points in a single year. What seemed common is that they (1) stopped spending time playing significantly weaker players, (2) began solo study for 2+ hours a day and usually with some expert guidance as to what they spent their time on, (3) developed a concise set of preferred openings as White and Black (making their study time more efficient; one player I know reached Canada's top 30 after restricting himself to Alekhine/Gruenfeld/Catalan -- boring game after game, but with these it's not easy for your opponent to force you into something else), and (4) spent time analyzing their games with experts and masters.
But this means you may have to give up some other things in life, and perhaps a board game isn't worth that. I reached a point where I was winning against experts, but began to realize that (lacking the brilliance of a true chess genius) I was unwilling to do what was necessary to rise much further. Other priorities.
You are telling me someone gained 700 pts in actual otb play? Unless they were sub 1000 I would have to see the documentation. If you go through USCF ratings on their website you will be hard pressed to find players who gained 300 pts in a year.
I wonder how long it would take me to break 2200 if I made a plan of it and took it seriously... that's the problem for most though, willingness to commit the time and energy.
This may sound stupid, but I have the impression that if you give me just 3 months with nothing at all to do, serving me food on plates etc, I might be able to reach that level. Actually participating in rated games and reaching that rating would take much longer though.
I think playing a 60 min game every day, analyzing it, studying tactics for 3 hours, either opening or endgame training for 1 hour and reading a good book for the rest of the 10 hour study period per day would take me there in 90 days.
Not to burst any bubbles, but if you studied 10 hours a day for 90 days most likely your results would get worse. I know because I have done it. There is a reason you don't see random 400 point jumps in rating outside the provisional period. The mind can only absorb so much, and no matter how much you increase your knowledge, it is the skill of applying it that you get tested on in tournament games.
I spent several months when I had a break from work studying and working with a GM - my results during and shortly after that period did not improve, even though I was long term becoming a better player. It takes a long time to absorb and manifest in your play new ideas.
With really focused study and playing 75-100 games a year of otb I would say an average talent can move up 100-200 pts a year up to Class A or so and then 100 pts a year after that.
So if you are 1400 now - I would say you are 6-7 years of really hard work from 2200. Almost everyone burns out on the work or gets distracted by other activities long before they reach that 7 years.