If you have photos or videos in a Picasa Web Album, the easiest way to still access, modify and share most of that content is to log in to Google Photos. Your photos and videos will already be there.
For those who have already downloaded it, it will continue to work as it does today. But we will not be developing it further, and there will be no future updates.
If you choose to switch to Google Photos, you can continue to upload photos and videos using the desktop uploader at photos.google.com/apps.