It would be real fun watching upscaled 480i signal on your 4KTV !! Enjoy !!! Anything less than original bluray will look crap on 4KTV.
With all due respect buying a 4KTV now is absolute waste of resources. You would be better off buying an OLED TV or heck one of the best Home Theatre projectors in the world for that price!!
Just imagine the bandwidth that would be required to transmit channels at 4k resolution. OLED is the next technology to wait for but it will not become mainstream in our part of the world for at-least another 3-4 years. Right now the cost is exorbitant to manufacture OLED panels. It would be safe to say the current technology is future proof for at-least 3-4 years. so anybody who is buying a TV need not bother about being future proof.
At present, we dont get much content in 1080i format and only 22 or so HD channels are available, so dont think 4k is useful for india, it would be more interesting to get 1080p OLED panels for both panel quality and also available content.
I think LG has already started taking orders for a test run of their 84" 4K UD Cinema 3D TV. As for Sony's XBR - 84X900, it will probably come by the end of 2012.