As far as the big display makers are concerned, Apple’s relationship with LG is probably the strongest.  LG makes iPod Touch and iPhone Retina Displays and Apple secured a $500 million dollar investment in LG displays in 2009.  The net of that was a temporary exclusive on the panels for the 27-inch display that Apple’s iMacs and now Thunderbolt Displays now use.

The other big OLED maker is Samsung, who is now tangled with Apple in patent disputes. If Apple does do a TV, it will likely have some sort of game-changer tech innovation that Apple could exclusively own for a period of time.  A 55-inch OLED would probably qualify even though yields will be low and prices will be astronomical.