i guess this is the most painful BC break for people who write their own blocks.

could we instead add a BlockContextServiceInterface with an executeContext interface and let the user decide if he wants the context things? we could then deprecate execute but make sure it still works the old way until a blockbundle 2.0 is released where we drop deprecated stuff.

for the cmf i don't care, its still time to do the BC breaks as we want the new options anyways and we are not yet stable. for specific projects, we should not need to care too much either, they can just fix the version of sonata blocks at 1.1. the real pain would be for reusable bundles that offer blocks that should be usable with more than one version of the sonata block bundle.
the dilemma is between cluttering sonata blocks with backwards compatibility and breaking everything. i don't know how many users sonata block bundle currently has? maybe drop the question on the sonata mailinglist who would see real problems with this?