No chance at all! If there is space in forward cabins and Y is over-booked, they may shift some passengers up, but preference is given to those with status.

The only way to guarantee an upgrade is to actually pay for it. Why should airlines give out free ones? Also remember, there are passengers in the premium cabins who have paid for the priviledge so how would they feel if Emirates were to give away free upgrades?

Emirates Y is a pleasant experience anyway if you can secure exit seats. If you ask nicely, you may get one at the airport.

Good luck!^
Simon