Knowing what we know about BioWare, I kinda don't want another "...It's a NEW beginning" game.
To me the perfect kind of "fourth" game would've always been a some-years-later "Aftermath" plot about how after the Reaper War, things are picked back up, and how a crippled council species society gets themselves back into the seat that guides the galaxy. In lieu of this I always imagined Batarians having survived, getting into trouble with the council species but ultimately thanks to a Batarian Squadmate, they earn a seat, and it ends with the galaxy having a bright, obvious future with remaining issues settled.
My biggest issue with 3's ending other than the obvious writing/logic faults at launch wasn't really that I felt too sad or Shepard's fate being somewhat inevitable... it was that I just wasn't ready for this, at the time, brand new Sci-fi universe to come to such a crushing end with so many unnecessary blocks thrown in that prevented it from ever evolving organically as it had before.
I get why they wanted 3 to be "it". But I just felt like the game steamrolled the future of the series unnecessarily, but with Perfect Destroy, or some subversion of all the endings, and without the "600 years later" Andromeda baggage, you really could've just made that one final game that reflects on the aftermath of Shepard's timeline, and end the series in a way that keeps all fans dreaming about future possibilities.