Depends where and when you fly, hub to hub you will be so for down the list you probably have no chance, but on the other hand small airports at inconvenient times it can be fairly likely. When I was gold I probably got upgraded 25% of the time out of BUF or to small airports I was travelling to, especially on the early morning flights.

As a Gold I also cleared a DFW - HNL upgrade on a widebody plane to lie-flat seats so sometimes you can get lucky too. But if you are not on the list then you have 0% shot of clearing.