Konami announced that an online beta session for PES 2018 will run for ten days from 20 July, but won’t be available on PC. It’s a console only affair, so the PC is left out.
The intent behind the beta seems to be testing online functionality, which you’d imagine would be worth testing on the PC version too. If I had to guess, I’d say Konami are paranoid about people digging through the files on PC. That’s usually the stated reason for withholding these things.
Konami have previously said that PES 2018 will actually get a version comparable to the PS4/Xbox One releases on PC this year. That’s a step forward from the PC version being a weird PS3 hybrid, at least. Sadly, it seems that commitment has not extended to including this platform in beta tests.
This online testing is separate from the annual PES demo, which will still be coming later in the year (closer to the September release date). Historically, the PC demo has appeared much later. We’ll see whether that changes for PES 2018 (probably not).