As a replacement yes, as a "new" (added) box, no.
Only HD boxes going forward (QIP-7100).
As keyboards said ... not as a new device. However, the 7100-series boxes will work with an SD TV as well as an HD TV. If you don't need the guide data or on demand, you can also consider the Digital Adapter which works with an SD TV and costs roughly the same as the 2500-series box did.