according to the splunkbase page https://splunkbase.splunk.com/app/742/ the TA is only CIM compliant up to version 4.2. We use CIM 4.6. Does it mean it won't work as expected. I asked because we are having trouble extracting the src_user field for most of the WindowsEvent:Security logs.
I've seen these issues before and it is normally when Splunk fails to update the CIM compatiblity in app, but it is technically compatible. The key thing to look for is "Splunk Enterprise" compatibility which I can see is compatible (i.e. TA 4.8.4 is compatible Splunk 6.6.x)
Also CIM is progressive and search time mapping. Which means, it won't break your system in worse case. Also Windows dataset has NOT been changed for quite long time.
Taking into consideration, I would almost put 99% confidence on TA for Windows with CIM4.6