There is NO way to be sure. You do not know if the airline is having a push TO upgrade people - so that they get the idea of what it is like - or if they are having a push to NOT allow upgrades as too many people have been getting them!
I have found that one certain way of NOT getting an upgrade - is to ask for it on check-in! It may be summed up by the words, "They have heard this one before"!