If Apple was to release new iPads in March, because of logistics, all suppliers will be already contracted to produce or prepare new parts, there will be leaks, already there will be test prototypes (its just 45 days before March!) and new builds of iOS geared toward new hardware, containing new drivers for newer chips, would be leaking. Since there is NOTHING, tells that industrial scale preparation for new iPads has not moved that far. Indeed, iPad 4 was released just 60 days ago.
So we'd better forget about March release for iPads/new mini.
Also don't forget that newer builds of iOS should already be iOS 7 builds and its been just few weeks ago that Ive took charge. I think beta of iOS7 will be ready by May; therefore June WWDC will be a bombastic conference on new iOS, new iPads, iPads mini, iPhone 6/5S and all other stuff. Its going to be an eruption (of stock too)