It really depends on the child.
DS1 was very obviously left handed from about 2 and a half, as far as drawing goes.
DS2 is the opposite. Id be extremely surprised if he ended up a lefty.

HOwever that said, whilst DS1 favours his left for writing/drawing/cutting, he bats right handed for cricket and teeball, but catches left handed (so with his right hand), and kicks a footy with his right foot.