Does it say anywhere why they changed MCU supplier? It'd mean they reprogrammed it, like when MB went from Intel to TI on Microvision games.
As well as the cost to reprogram the game for a different chip, they had to redesign the PCB, so there had to be a good reason.
I'm guessing there weren't enough COP444's available. Handheld Museum says over 800,000 games were produced. I bet it sold better than expected and they had to scramble to keep up with demand.
But that doesn't explain why they changed the case. It seems like they would have used the same molds. Maybe there was some rights issue, and they owned the general design but not the specific implementation? Once the game took off, it was cheaper for them to redesign everything?
I found some interviews with Rick Dyer, but they pretty much skim over the handheld games he worked on and concentrate on Dragon's Lair.
Oh, and I picked up a Speak and Read.