Best option is to call skywards.. and check if there are seats available on the dates you are traveling..

ask them how many seats are available.. some will give you an idea.. some wont.. so call back until you have a rep who will cooperate with you.

keep in mind there is always a risk of losing the upgrade.. i was on the phone about to upgrade myself.. and before the rep finished her sentence.. she said "oops.. sorry someone just snatched it"

if your dates are flexible.. pick dates to travel that normally don't fill up so fast.. weekdays are easiest.