3 cycles of what? Even if you did 3 cycles of Sdrol and kept 8lbs of each that'd be something REALLY good. even more so if 8 of those pounds were ONLY muscle. Plus then when you cut you will lose a lot of it. Also, the stress and damage on your liver from that long usage and the damage of using all those SERMS.... While I will say that yes the natty will probably get around 12-24lbs of "mass" on from a year depending on where he is on his training age, someone who uses AAS will definitely get bigger faster, but a lot will by lost because of water weight initially, then when they cut if they don't have the AAS in them the body will not be able to support the extra muscle for too long while in a calorie deficit. I'm not sure on the science or what not but I am sure Alan Aragon (Who I don't particularly agree with on everything), said just like how the body has an essential fat/non essential fat level there is also a level of non essential muscle. And w/o the high levels of anabolics running through you you will probably lose most of it.
The guy might come out maybe 2lbs heavier than the non user.... It boils down into this really, why are you taking it? In this business there really is no "cheating". Everyone has access to everything, as long as they know what they are doing. If you compete natty just don't take it. The guys know they'll never get as big as Jay Cutler, they probably don't ever want to. But they know they can get pretty jacked w/o the PH. Guys that take the PH know that they will never get as big as Jay Cutler, but it's fun to try. And also, if you're not competing and don't really care about all the gray area trash talk, it's not that bad for you... As long as you know what you are doing, take your blood tests, take your vitamins, and live/eat healthy.