The program would stop, but the files would remain on your computer. Before stopping, you could do a batch convert to tiff or png, with a strong recommendation for tiff. Png only support transparency whereas tiff supports layers, live type, transparency, etc.
Keep in mind the app you open the tiff file in may not support all of those features, but it could if they tried.
The psd files I would backup to a cd or dvd before removing for space, but if you have the room, keep them as some apps do support psd files.
Best part is when you are ready, you can start your subscription again and use all of those files once again.
