The A300 series could easily be mirrorless, now. That reminds me. Some time ago we discussed some of the more cynical aspects of technology development. Minolta users in the 1980's had to buy a whole new suite of lenses for the autofocus mount, as the MD lenses were of a different size and bayonet mount. Now, if the Nex cameras intend to replace the Sony A / Minolta AF mount, then we would need to replace our lenses again. Result, more money for Sony from those who want to stay with the pedigree.
However, at this time, it's a little hard to see that the Nex could replace the A900 level of camera. In fact, Canon and Nikon are having troubles catching up with the A900 still, after a couple of years after the release of it.
It seems that Sony is trying to get in on a niche market. Here in Japan, people love cute, and especially young ladies and families. They want something that's a little different, but they don't want to go for an unknown or lesser brand. So, it seems that the Nex is aiming for a particular market of having something a little different, a new style (even though the Olympus Pen had been there before), and being family oriented, without being as ostentatious as an SLR. That's my take on the Nex camera.