Konami has released a statement confirming that it won't be renewing the licenses for both Milan clubs, namely FC Internazionale Milano and AC Milan. While the presence of both clubs will remain unchanged in eFootball PES 2020, Konami had the following to say regarding the future:
"In regards to other KONAMI football games, please wait for future announcements for each title."
Now, we don't how the Serie A license works, but this likely means the two Milan clubs will not appear in a licensed capacity in PES 2021. There's also the matter of the shared stadium, the Giuseppe Meazza, and the presence of legendary players from both clubs in MyClub mode. We guess more will be shared when Konami eventually announces PES 2021.