After watching the noncanonical endings of Shadow the Hedgehog, I wonder how much the timeline will be skewed if they were canonical. So I pictured what an alternate future might be. I will also give my odds of how much these endings are canonical to the true ending. Keep in mind though, I'm not gonna use spoiler tags. So if you don't want to be spoiled, turn back now. You've been warn. I'm starting from the darkest endings to the holiest ones. Here we go:

Pure Dark with Dark Ending: Shadow basically goes insane with evil. He's bent on destroying the world he thinks is inferior.
Alternate Future: Think of either Black Doom's true plot or the world blowing up (that's what I think.) Basically the Earth is doomed either way.
Odds of canonical: I think is about fairly low. For one thing, Shadow beats Sonic. Two, he carries such a tainted hate for the world that even if he finds the truth, it would be too late

Pure Dark with Hero Ending: Shadow overthrows Black Doom and becomes the dictator of the Black Arms. Shadow decided he was created to conquer the universe.
Alternate Future: Well, since he didn't know about the truth of the Black Comet, Shadow will try to conquer the Earth his own way. The war will still continue and who knows who will win.
Odds of canonical: Low. During the opening of the final story Black Doom orders Shadow to give him the emeralds. Now, Black Doom wouldn't be doing that if Shadow kicked his butt.

Semi Dark with Dark Ending: Shadow says he's a loyal servant of Black Doom. He is a servant, body guard, butler, etc.
Alternate Future: Think of my darkest path theory. Except this time, if Shadow found out the truth, he probably would save the world or he might end up to loyal to Black Doom. Remember, loyality is one of Shadow's strong points.
Odds of canonical: This is probably one of highest chances, but I think it's Mediorce at best. It's still IMO that Sonic, since he's the hero, should be the best.

Semi Dark with Hero Ending: Shadow simply says he will do things for himself. He doesn't save or destroy the world. Heck, he doesn't even mention the emeralds. Oh and he kills Eggman
Alternate Future: This seems like a true neutral ending to me. The war will still continue. Again, with Shadow not helping either side, who knows who will win. And with Eggman gone, his empire will be up for grabs. Most likely by Omega or Metal Sonic (if he's still functional)
Odds of canonical: Absolutely zero. And it's all because Eggman died.

Neutral with Dark Ending: Shadow thinks he's an android and tries to be better than the 'original.' He kills Eggman.
Alternate Future: See above theory. Except this time Shadow MIGHT find out he's not android.
Odds of canonical: Absolutely zero. And you know why.

Neutral with Hero Ending: Shadow still thinks he's an android and he shall lead the Eggman Empire. Shadow kills Eggman
Alternate Future: Shadow now runs the Eggman Empire. And I'm assuming Omega will be 2nd in command. Now he have a valuable army but I think he will focus more on the androids than the robots.
Odds od canonical: Absolutely you-know-what because you-know-what-happened.

Semi Hero with Dark Ending: Shadow proclaims himself as guardian of the ARK. He thinks it is to sacred.
Alternate Future: Well, if there are any future games with Shadow now there wouldn't be if this was canon. Shadow will simply guard the ARK like Knuckles guards the Master Emerald.
Odds of canonical: Fairly high. Eggman lives. Black Doom will tell him what's what. And it might continue from there.

Semi Hero with Hero Ending: Shadow thinks his existence will bring nothing but pain and misery. He sounds depressed and thinks he's a research experiment gone wrong
Alternate Future: Ohh. Shadow isn't exactly happy. Thinking your birth will only contribute pain, not meaning, to the world can do some things. Shadow might commit suicide or destroy himself emotionally. I don't even think a Shadow hater would wish something like it
Odds of canonical: Low. He defeated Black Doom so he might not continue as in the final story.

Pure Hero with Dark Ending: Shadow now proclaims himself as the ultimate hedgehog. He enjoyed beating Sonic for heck of it.(Even if Sonic had a disavantage. He had a giant robot on his side. And we know how they are.)
Alternate Future: Great, now Shadow will be more arrogant. Beating the main hero will do that to you. Now I think, to a degree, Shadow would be main star. Ugh.
Odds of canonical: As much as I hate to admit it- high. Eggman's still alive. He didn't attack Black Doom.

Pure Hero with Hero Ending: Shadow recalls a promise he tends to keep. He drives out the Black Arms. Order is restored. Everybody's happy.
Alternate Future: Expect a smooth sailing here after. Shadow kicked butt. Sonic is still number one. Things will continues as smoothly.
Odds of canonical: Eh. It depends. If Shadow didn't get amnesia in Sonic Heroes, the odds would have been high. However, going with the Shadow game, it's low. He beat up Black Doom.

Well, that's it. Feel free to add some things. Criticize (constructively) Thoughts and opinions would be nice.