Both the level of chess playing strength and the number of very strong players at the top have increased over the past couple of years or decades. Looks like Magnus achieving 2851+ some time soon could very well be possible.
Both Magnus Carlsen and Levon Aronian have been showing a great performance in Wijk aan Zee this year. Who knows, maybe Magnus even manages to surpass Kasparov's all-time best already in this very tournament, while still coming in second behind Aronian in this tournament? Nothing seems impossible
According to the latest updates of players' ratings from http://www.2700chess.com/, it is officially stated that Carlsen has reached a stunning 2841.6 rating after beating Boris Gelfand. After all, Carlsen was an international master at the age of 13. Will he achieve 2851 one day and surpass chess legend Kasparov?