I'm not sure if it will go away. The unlock code may need to be embedded in the file before sending to the GPS. But as long as the birdseye file is on your computer in basecamp, you can delete it from the GPS and send it again after subscribing.
In my experience, when you send a file without a subscription, you will get that message, but you can still view a small part of the file as a sample. IIRC, an area of about 1 mile x 1 mile at the center of the image will be viewable on the GPS.