While Google Photos makes a lot sense, replacing Blogger with Google Blogs is not a great idea. When people say "Google Blogs", they refer to the long list of Google's corporate blogs. "Google Blogs" is already used for Google Blog Search, but only on the homepage.
On the other hand, Blogger could be redesigned and use interface elements from Google+, Blogger's profiles could be replaced by Google Profiles, the commenting system could be revamped and integrated with Google+.
One of the reasons why Picasa Web Albums didn't improve too much is that it has always been perceived as Picasa's online extension. It wasn't a standalone photo sharing service and many of its features required Picasa. You couldn't upload more than 5 photos, download albums or edit photos without installing Picasa. Google considered changing Picasa Web's name back in 2008.
