The legislation defining different categories of vehicle for driver licensing purposes is set at EU level, and applies in all Member States.
EU legislation therefore defines categories B and B1, as well as all other categories. However, EU legislation specifies that, if a person obtains a licence for category B, they shall automatically qualify for a licence in category B1. The reverse does not hold true - category B1 licence holders are not automatically entitled to a category B licence.
I am unaware of any plans to change this at EU level.