Smarthouse (responsible for a lot of rumors lately) are claiming that Sony is working on a new 'secret' TV technology. This new tech is not OLED and not LED backed LCD, but rather a 'spin-off technology' that is reportedly easier and cheap to make than current display technology. It is also power efficient. Smarthouse say that this new technology is the reason that Sony decided not to release a new OLED TV.
Smarthouse says that they talked to a Sony insider who told them this. They also base this on an AP interview with a Sony executive a couple of days ago - but personally I think that they mis-read that interview. The executive indeed says that Sony needs their own technology, but he is talking about the ability to make their own TV panels and not buy them from Samsung like they do for LCDs.
It's possible that Sony are indeed upgrading their OLED TV technology, making it suitable for larger panels. They recently stopped their pilot production line, which was loss making, and are supposed to launch a new larger OLED TV soon (the KDL-ZK)