Yes it is. He could do it by beating The world #2 and #3 like 20-0 in a rated Blitz Deathmatch or something of the sort. His "live" rating would reach 3000 although his rating would only reflect when FIDE did their official monthly posting.
Chess Ratings....
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Is it possible for a World Number one, lets say GM Magnus Carlsen to reach 3000 elo one day??