Hi,
Thank you for your message.
CodeWarrior Development Studio for HCS12(X) Microcontrollers (Classic IDE) v5.2 is the latest official version currently listed by NXP for this product line.
So, if you have already downloaded CodeWarrior Classic 5.2 for HC12 / HCS12(X), that should already be the newest available release.
Please refer to the official NXP product/download pages below for confirmation:
Best regards,
Ladislav