As quoted from the site Mashable.com Picasa will be renamed Google Photos and Blogger will be renamed Google Blogs, Picasa is a provider of online photo albums while Blogger is a free blog service providers. Such rebranding step is not only the first time does Google. For example, when it acquired GrandCentral VoIP service in 2007, later changed his name to Google Google Voice in 2009 as provided to the public.
In addition, the rebranding will strengthen the Google brand. Picasa and Blogger users so far probably do not know if you use Google's products to enter despite already being forced to use a single login address.
Picasa is a product of the acquisition in 2004, but his name is not changed then. So is the case that Google bought Blogger from Pyra Labs in 2003.