Ownership change probably only necessitates chip change if the name AND licencee changes.
Look back at Aladdin/Planet Hollywood. For some obscure reason I followed the process through the NGCB minutes.
It took 18 months from the time the ownership changed to when the new licence was issued. All the chips issued during that time continued to be Aladdin chips, albeit with "PH coming 2006", "PH coming soon" etc etc on the back.