In the Blogs Update Phase 2.2 in April we added three new themes.
We also retired the Spectrum News Theme.
We have now retired the Suffusion theme too.
Existing blogs that use these themes will continue to do so. They will not be able to be selected in the Theme chooser for new or existing blogs. We will turn this theme off completely at a later date it would be wise to change themes before then. We expect Spectrum New to be completely disabled by the end of 2015. Suffusion, being a very widely used theme will be deployed for longer.
Both of these themes are showing problems with our newer version of WordPress. Features have broken. The updated version of Spectrum News did not work with our multi-site WordPress install and would have required considerable work both now and over the longer term to keep it going. The suffusion theme developer is having trouble keeping it up to date, it is also showing some problems with our new version of WordPress.
We hope to have a few modern flexible themes in a release soon. We are also producing some guidance on moving from these themes to TwentyFourteen: Spectrum News to TwentyFourteen. Another page covering Suffusion will be added to the help blog over the summer 2015.
If you are using the Spectrum News Theme we would advise that you look to changing that theme as soon as possible.