I may stay. Though looking at the list of new features below still not convinced, and there's no guarantee that the fee will not keep increasing, due to 'new features' being added. I have ~4500 images, but most are 'not doing anything', and it's by no means a complete back-up of photos.
Pros get these perks:
Unlimited Storage. The only limit is your imagination. All Pros may now upload as many photos as you can take, always at full resolution.
Ad-Free Browsing. Focus on what matters with a fully ad-free Flickr experience for you and your visitors.
Advanced Stats. See which of your photos are trending now, and which have performed the best over the life of your Flickr Pro account.
Plus all these great new Pro-only features:
Premier Product Support. Skip the line. Flickr Pros now receive priority assistance from our new world-class support team. Available now.
More Partner Discounts. Save on photography essentials. Discounts on Creative Cloud from Adobe, 50% off a custom portfolio site on SmugMug, gear from Peak Design, and more. Coming November.
Advanced Stats on Mobile. Stats in your pocket. All the photo stats you know and love, available in the app. Coming November.
Increased Exposure. All Pro members as of January 1, 2019, are eligible for priority exposure in the next iteration of Explore. Coming early 2019.
New 5K Photo Display Option. Look your best. Your images are beautifully optimized for any screen, from smartphone to jumbotron. Pro images display at resolutions up to 5K. Coming early 2019.
10 Minute Videos. More time to tell your story. Play back videos for up to 10 minutes, increased from 3. Coming early 2019.