The cartoon that accompanied the GO! line in Japan, has ended, and some screen caps have been posted here.

The cartoon was short-lived, and short of length, with only 4 or 5 episodes, of about 11 minutes each long.

If I recall from a promo disk I got from Japan, it only features the Japanese exclusive characters (the new moulds and the beasts with new heads or completely new colours).
This final episode looks to feature the Exprime Optimus that was released in January (train & dragon modes), and combining with the leaders of the two combiners from GO!

That should pretty much confirm that Exprime Optimus was indeed the last of the GO! toys from Japan... and possibly means we won't see the EZY Groove toy either.