A quick check of the Northwest press releases indicate things are hunky dory right now. A settlement with the simulator technicians was reached today. The flight attendants reached an agreement on Monday.
I have friends and relatives in the airline industry, including Northwest. I’m betting the settlements were reached because the union strength at Northwest is very low. The maintenance workers went out on strike last winter and lost. Some got their jobs back at a lower pay scale. Many never came back. The kicker was the pilots agreement back in March. Had the pilots gone on strike, the airline was set to permanently close its doors. Northwest probably used that carrot with every other union issue since.
But getting back to you OP, you should be fine. If there was/is a strike, the value of your ticket would be determined at that time. You might get a refund and you might not. Other airlines might honor a ticket (if you were enroute at the time) or they might not. The volatility of the airline industry is so tough right now that any comment would be pure speculation.
One thing for sure, you can forget buying flight insurance. Northwest is in bankruptcy and flight insurance is not available on bankrupt airlines.