Unlikely. If RSGP drops that low, simply means the EoC failed, Runescape would be on the brink of death. Unless somehow, there is mass deflation, and mills are not needed.
Is highly unlikely to reach that low as there are currently simply to many players so like said above we would have to see a massive deflation in a short period of time to see it that low .
I think rsgp will raise it's prices, as runescape turned to mainstream game where many young, rich idiots will start playing who'll buy tons of gp to succeed in game