No likely about it, they will cancel any remaining segments on an itinerary if you no-show a flight. Your question pre-supposes that you are buying a non-refundable (cheap) fare. Any changes to that ticket after purchasing opens you up to massive fare changes depending on when you do it and what you are doing to it. What you are talking about is not a simple date change, but routing change and most airlines (since you don't mention which airline, but your post shows NWA, I'm assuming you're talking NWA and other legacy carriers) DO NOT allow routing changes on non-refundable fares. You would have to cancel the existing ticket and start all over again. Worst case scenario is if you do this change in the middle of your trip, you may have to buy a one-way ticket home.

So, consider carefully what you are trying to do before you commit.