To check current status you can text the word 'upgrade' to 1311.
Also, you can log into your sprint account on their website and I think you can hover over your phone icon to see current upgrade eligibility or view your contract details if you aren't currently eligible.
As I had posted on the other thread, I have been under the impression that everybody gets the full upgrade after 2 years unless you are the primary line on a Premier Account (I don't know the requirements to have that status).
Hopefully somebody can either confirm what I've posted or give updated information.