The intent of the Jagpanzer unit was to capture everything in this category (later war STGIII and STG IV as well as Hetzers, Jagdpanthers, Jagdtigers, Elefants, etc.) - all of these units are captured by the 4-7 jagdpanzer unit. The early war assault gun 4-4 units (short barreled anti-infantry assault guns) are replaced by the longer barrelled, largely anti-tank version of the assault gun.
So - I don't think the 4-4 should be continued after 42, instead, StuGs are up-gunned and up-armored to 4-7s later in the game.