Nobody can prove anything really. The console war is every bit as fictitious as the war in Iraq. We can sit here on our forums and debate this until we're blue in the face, but we can't truly predict anything because there is no way to predict upcoming trends. The only people that can truly make a valid prediction are the companies themselves because they know all the things coming down the pipeline for their systems. And they hold those cards close to their chests so that they have things to trump each other later on.
The 360 isn't going to just automatically win because of good sales and an earlier release, BUT one thing we do know is that it has now officially taken a big chunk of market share away from Sony. That's not a prediction we need to make, that's something that's already happened. No matter who comes out in first, second, or third this generation, Sony is not going to be the dominant force that they were with the PS2.
And the PS3 isn't automatically going to win just because it's a BluRay player with the Playstation brand on it. If you think the price tag of the PS3 isn't a big reason for people getting scared away from buying it, then you're delusional. When the holiday shopping season is upon us, there will have been a permanent price cut on the 360. Not a fire sale, a permanent price cut. Holiday shoppers buying consoles are mostly parents. The way the economy is right now, which console do you think a parent is going to choose?
You see kids, in the real world where people pay bills, mortgages, gas, etc. every day and try to scrimp and save until the mortgage/gasoline/food crisis is over, the $399 game console their kids want may not be #1 on the priority list. But the $299 one might be a better option, or maybe even the $199 Arcade model. Or maybe even a Wii.
The console with the most things up in the air right now as far as the future goes is the PS3. It's the highest priced with no price cut in sight anytime soon and is not selling well in its bread and butter market, which is Japan. Oh, and despite its good numbers so far this month, I would also like to remind PS3 fanboys that yes, the PS3 is still in third place. I know, I know, it was supposed to have passed everyone else up by now......but it hasn't. So now we're going to start hearing what date in 09 the PS3 will pass up the 360. It was supposed to be summer of 08, but that didn't happen. Now it's supposed to be holiday 08, but that's not looking very likely either. So I'm guessing that soon people are going to start saying summer 09/holiday 09 pretty soon.