Anyone has news regarding when this update will apply to devices in Singapore?
It should arrive somewhere Apr-May 2014, or even later.
My personal opinion - If you are still on 4.1.2, stick to it. Flash a custom ROM if you want to get 4.3 or even 4.4 (CyanogenMod is a good choice)
Whatever you do, DO NOT get any more official updates from Samsung from 4.3 onwards. Why? From 4.3 onwards, Samsung will introduce a new KNOX bootloader that will make downgrading to older version impossible. Rooting and flashing custom recovery/ROM will permanently trip the KNOX flag and void warranty.
Of course, if you are just an ordinary end user and not into all these stuff, by all means OTA update when 4.3 is ready by Samsung.