According to Wikipedia there are eight generations of video game consoles, each generation defined by the consoles that are released and the innovations they make. We are at the start of the eighth generation with the PS4 and  Xbox one about to hit the shelves this month.

Releasing a console is such big business that the money made from the console purchase itself is negligible. Often sold at a loss console developers will instead be hoping to cash in on much more, including licensing fees, monthly subscriptions, video steaming rental and advertising.