Should I get Diablo II when Diablo III is coming out soonish?

You are way off with that guess. Blizz tends to release info on games very early and even though it may seem like ages since it was announced the game is not yet finished. For a guess I would say 2012 at the earliest maybe even 2013. There are rumours of a console port so it may take a while for the game to be released. Diablo 2 is good fun. The multiplayer has stagnated recently as the game is over 12 years old but still worht a look