Damn i haven't read the novels yet, got to get my hands on them as well :D
Cerberus was one of the associations that was least explored in the game but you could really feel that they had a grip on many things in the galaxy, so they playing a big role in the continuation will be a good thing to expect.
I didn't know that most people didn't realise that there was another force at large in the Citadel attack, mainly because the appeareance of Sovereign would have raised many doubts as wether if that could be another Geth construct or something different whatsoever.
Also there were other recordings of Sovereign, even in the attack of Eden Prime you could see him appearing in the Sky.
But that could play well in the role of the next game, because if people aren't expecting another force greater than the Geth, then that can give an impulse for an appearence of another agent of the Reapers, just like Saren. Or we can see a bunch of Indoctrinated subjects appearing in the second game as well.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
