Let me make this clear.
To upgrade, they cancel and redeposit your miles, then they subtract the amount for the F award.
They do this for free, but that doesn't mitigate the fact that they cancel and redeposit.
To illustrate this, take a look at the account history where an upgrade has been done, you'll see deposit of J prices and subsequent subtraction of F price.
This leads me to believe that it will be highly unlikely that upgrades will be prices at the old chart, but who knows.