Correct me if I'm wrong, but don't we see in the Peacemaker S2 trailer that he meets his DCEU counterpart? Thus, tying the two universes together?
Additionally (and this is unfortunate), James Gunn has stated that he doesn't really care about continuity or timelines and wants to focus more on...
Well I watched it and I didn't hate it! I DO hate all the songs but it's a solid movie. Very artful. I can see why people may have been disappointed coming out of the cinema watching it but I think it's highly underrated.
I think what Gunn was trying to say is that if you don't agree with his canon he doesn't care because it's all fiction anyway. However, he is trying to create a distinct canon for the DCU.