KH3 will (definitely) come out this gen.
It can be announced any day (not exactly any day, but at any major gaming event) - since it's not a problem for SE to announce a game that they havent started developing yet, they do that all the time (recently - FFCC: Crystal Bearers, Dragon Quest X) I am expecting the KH3 announcement this year.
Another thing that suggests there will be KH3 this gen is the company's strategy they are using since 2005: when it comes to their big franchises, instead of developing an independant game each new time, they instead make each such game a part of some planned project/compilation, with one main title and a number of spinoffs to support it - they do that with Final Fantasy (Fabula Nova Crystallis), they do that with Dragon Quest (DS remakes of IV-VI, DQ related games for DSi), they are going to do that with Eidos' IPs, and the three upcoming KH spinoffs suggest that they are about do that with KH aswell.







