aight, i didnt read this whole thread, just came to the last page to put my 2cents:
i do believe in the IT theory...they've hinted at it in the game and in real life....
in game:
1. the kid - shepard was the only one that saw the kid....reason being the kid was a ploy by the reapers to get shepard on thier side...humans have a soft spot for children, reapers would know this, they're an advanced being....which explains why the godlike figure trying to get you to work with the reapers at the end was the same kid...
2. the ending choice colors/explainations by the kid - the colors for good/bad choices were switched...destroy, which was the good choice, was colored red...and the kid made it seem that was the worst choice you could make....while it was the opposite for control and synthesis....
3. Indoctrination. - looking at the indoctrination def and the symptoms associated with it, shepard was experiencing this throughout the whole game: the growling noises, the nightmares, headaches, etc...the kid's reaction to whatever choice you made represented the reaper's reaction...if you picked destroy, he disappeared instantly, meaning they knew they failed...the other choices, he lingered around meaning they knew they succeeded....
4. extra scene - it showed that shepard never left earth to get on the crucible and that he was alive....which means the whole thing on the crucible wasnt real, and in his head...
real life:
1 bioware staff - they've been quiet about all this for the most part, except 1 important thing: telling us to keep our saves....why would we need to keep our saves if this was the last game?...they could, but i doubt they're gonna release major dlc for this game that our saves would be important for...our saves are for the next game....
...i think they started out and intended this to be the last game, but EA and them realized killing this cash cow now wouldnt be best for business....the problem was though they had spent so much on marketing already about this being the last game, they couldnt change that....so they just stuck with that marketing scheme, while knowing it wasnt true...and are gonna announce me4 with shepard still fighting the reapers...but now, there has been a turning point in the war, cause the reapers couldnt indoctrinate shepard, and it scares them...