I agree & I certainly do not want to upgrade to ADE 4! However ADE ACS4 DRM does appear to be what Google Play is using. (See the Copyright section in the link below.)
https://play.google.com/about/books/...tml?hl=en&rd=1
I do not believe ADE 2.0 supports ADE ACS4. If I am wrong I stand corrected. All I know is I have ADE 2.0 & I am getting an error message that is preventing me from downloading new books. I am just trying to find a way to fix this. Per my question, does anyone know if both ADE 2 & ADE 4 can coexist? If so, which version will open automatically when you download a book?