That is about desktop Windows 8/8.1, not Windows Phone.Not sure what they me by this : Microsoft News | Microsoft Extends Windows 8.1 Update Requirement Till June 10th
There is no official date as of yet. People are speculating its end of June since MS came out with their statement that WP8.1 support cycle will begin 24 June 2014. So all you can do at the moment is patiently wait.
I have installed WP8.1 Dev Prev on my Lumia 1320 and region is India. Its pretty stable except for a few bugs here and there. So I would say you can give it a try if you feel the wait too long.
Guys,
Has someone got any official cyan update on their mobile for Lumia 1320 in india...