No question that there will be extra story DLC to actually complete the story..for a price. That or, some "epilogue."
Frankly, some of the endings just do not appear consistent at all with the series, especially Synthesis(magic ending?). Sovereign in ME1 made the Reapers appear like a collective of hyper intelligent beings (each a nation, etc etc). In ME3 they appear kind of stupid. All the subtly and patience of Sovereign thrown by the way side. Hell, even Harbinger used the Collectors, so I am not sure why all that was forgotten by the Reapers, especially since they waited generations to properly kill the Protheans.
About the planet with the 2 moons,