Elo 4312?


I didn't do the math, but if he kept beating all of the highest rated people, eventually there would be no one left to raise it higher quickly. He could reach around 3500 though.

http://ratings.fide.com/card.phtml?event=14926970
This player has elo 2114 on March and the next month 2540 (!)
So, if player has elo 1001 and win all game with player who have over than 400 points and he has 18 yers old he won 36,8 points per game. If he play 90 games (3 games per day) the next month elo 4312. If start 2399 he must win with over than 2798.