You are forgetting that MP, despite being financially successful, left ME3 with a rather blackened eye thanks to the EMS thing.
They have already decided not to include DLC companions with DAI because of negative feedback brought about by Javik. Is it no treasonable to assume tehy would modify MP policy for the same reason? Either forgo it entirely this time or make it a truly separate install for the sake of rebuilding their relationship with their fans?
The issue- as you pointed out- is that the multiplayer affected the single player story. If they're going to stop doing anything it's that. The multiplayer mode itself was very successful for the company and obviously a lot of players enjoyed and are still enjoying it. Because of that, I would count on multiplayer making increasingly frequent appearances in Bioware games, even if it doesn't make it into DA:I.
That's my objective opinion on the matter.
I would suggest that you likely overestimate the number of people who felt that their 'relationship' with Bioware was damaged because of the inclusion of Multiplayer- barring the Galactic Readiness issue. Even then, my guess is that- of those people- most would be content if Bioware simply designed a multiplayer mode to not influence the single player campaign in any way, assuming the SP campaign is also considered good and fulfilling.
Finally, I'd guess that the number of people who would actually be satisfied by seeing MP divided off into a separate install would be dramatically outnumbered by the number of people who will play both SP and MP and would prefer that both modes are readily available upon the game's initial install.
Nevermind the technical nightmare and inconvenience it would probably be for devs and players alike to actually separate SP and MP on 5 different platforms.