Yes, according to content designer Kevin Martens there were plans to transform the game to the full MMO and not that long ago. But this information is no longer true and there are no such plans right now. Reasons behind this decision are simply players and the corporate culture. Players were playing and enjoying the game like it is therefore the need to transform it is not viable. However future content remains untouched and in the development.
Diablo 3 – considered for an MMO?
Diablo 3 - considered for an MMO?