According to the brand new Google Merchant Blog, Google Base is finally being replaced with the Google Merchant Center. This move has been expected for some time, and Google introduces it saying:
(The new Google Merchant Center) will replace Google Base for those of you submitting Product-type items to Google. If you submit products to Google, Google Merchant Center is now the place to upload your feeds, check on the status of your items, and get information on the performance of your listings.
They go on to assure people that Google base isn’t being completely shut down – yet.
Google Base is still available for other types of structured content, but the Merchant Center provides a better, optimized experience specifically for product listings. The Merchant Center is where we’ll continue adding features and improving the tools for uploading and managing product listings.
This generally is accepted to mean that in time Base will fade out of the picture – Google doesn’t keep things around that are outdated. There is a transition period, though, obviously. For non-product items, Google says:
For any non-product items you’ve submitted to Google Base, those will remain there and you can continue using Google Base to manage those items and settings.