I've tried searching for this and found no answer, I've also submitted a support ticket and even though this should be an easily answered question, I didn't get an answer from support, I got the response to come back here:
We have versions of pega spanning 6.1, 6.3 and 7.1 that run on versions of WAS that are listed as supported by pega when they were created. Recently we received notice from IBM that some of our WAS versions are going out of support. Does this affect anything regarding pega's support for those platform combinations, i.e. does IBM WAS out-of-support status affect pega's support status for those pega products that run on them?
The status of WAS support does not affect PRPC or Pega Platform support. We will continue to provide support for PRPC and Pega Platform even if IBM is not supporting the version of WAS that you use with it.
Of course, we cannot provide support for WAS itself.