I spoke with the Electric Quilt people. You cannot export project files from Blockbase+, so EQ8 is needed in order to incorporate blocks from Blockbase+ (new version) into Electric Quilt.
With the old program, I can save each block as a project and open it in EQ7. So I'll stick with that instead of upgrading.
Just writing out my final resolution for posterity, in case someone else has a question about it.