Hello Collin,
Normally you should not be transporting between systems with different software versions. STMS warns you and do not let this. But if you are "%100" sure what you're doing, you can ignore this and continue to import. In order to ignore software mismatch, edit the transport options in the related transport window. But as I said, it should not be the case.
After upgrade, you'll have en EHP7 system but the previous requests will remain as EHP4 change requests. The previous situation still applies.
Regards,
Serhat