I would not be very optimistic. I had a similar situation in my flights to FRA/DUS from DTW, and return. On the way over, the agent refused any kind of upgrade at all... operational or mileage. There were only a few seats in Business, but they remained empty.

Coming back on KLM, the agent said "NO", then said "Go out to the ticket counter and try." Now that was quite a trip. After standing in line about twenty minutes, the KLM agent said "Of course there are business class seats available. But the only way you are going to get one is to buy a one way business ticket." About three fourths of the KLM business class seats remained unsold, but even at boarding time they would not allow use of mileage for upgrades on a discount fare. "It is a revenue issue," the agent finally explained.

The good news is that I found Northwest coach greatly improved, and KLM coach surprisingly adequate. Two empty seats beside me certainly helped. If you don't get the upgrade, ask at the desk if there is any seat with an open seat next to it.