How long until OSX is integrated into the iPad?

Looking at what Microsoft is doing, integrating the Desktop as an option into the Pro variant of their Surface tablets, tech lovers are drooling at the futuristic idea of just being able to have a tablet on the go and a desktop if you plug it in to your display & peripherals.

Having an iPad plug in via Thunderbolt display would be a really great step forward in portability and consolidation of ones devices.

will pair it with “much upgraded hardware specifications and integrated applications.” They’re designed to better compete with Windows 8 tablets expected in Q3 this year

Who knows if those older reports are anywhere near true, but the question is - how long until we see the inevitable merger between iOS and OS X (...OS XI?) 2013? 2014? Less or more? How long until we see the processing power capable of pushing a, at the least, MBA-type experience on the desktop packed into a tablet form factor?