"ipad 4" really means "iOS 6"
They'll release a new iPad in the spring and a new iOS version in the autumn. So yes, it gets an upgrade twice a year - once with new hardware, and once with new features curtesy of the software update. iOS 6 will certainly make it even more competitive with windows 8 tablets, so that makes sense too.
In that sense the "iPad 3" rumour was kind of right just a little bit too - the iPad 2 did get upgraded, new features, speed improvements, etc.