It's really impossible to say at this point. It's almost certain that Sony will do much better in Japan, however if WiiU becomes the next-gen system of choice there (which I think it will), it could put Sony at a huge disadvantage if Microsoft takes the US again.

One thing's for certain: The Xbox brand is far stronger now than it was starting this generation...

I don't know exactly who will win or lose next gen, but I will say one thing: Microsoft is NOT going to kill Sony. Such a ridiculous statement. I'm considering reporting you for intense ignorance. You can't kill something that's already dead. It's called "Playstation 4" (Japanese translation: "Death of Playstation") for a reason.

WiiU
But between the two options, I'll go with xbox720. The Playstation brand seems to be slowly dying.

the PS brand is in a far worse position then it was in 2006 guys. PS Brand was at no higher point then in 2005 when the 360 came out, now with the PSP fizzling out and PS Vita struggling, the PS3 in 3rd place it's hard to argue that Sony has some kind of advantage here. Each generation can totally change things just like it did this time around so anyone can win and we have no info, but Sony at best is on equal ground right now with Microsoft.

It depends you never know if the PS4 will come at the reasonable price of just over 599.99 US Dollars or if the NextBox will have little first party support hmmmm... I'll have to go with the PSFo. Sony might actually have really good titles and they might (well...) not shoot themselves in the foot again with over doing it.

i would say next box in terms of sales

the 1st few years this gen werent nothing to write home about but once they releases there 3rd console they'll have better 1st yrs than last gen b/c of the established base and franchises, they also have more room to grow in europe and even japan

i feel sony would need to release at the same time or earlier, have a dev friendly console and releases more M rated exclusive games in the TPS and FPS genres for them to have a chance

My vote goes to the next Playstation. People talk waaay too much trash about the Playstation brand. They have a lot more exclusives (high quality ones too) a very similar online system minus cross game chat (and the Vita has this so i'm guessing Ps4/Orbis will as well) and it's free.

In terms of sales PS3 has been outselling the 360 for years now. 360 just had a year headstart and cheaper pricetag. The new Playstation is rumored to be more dev friendly, which will help with 3rd party AND their already impressive 1st party teams.

Players in Japan and Europe both prefer PS3, Only in NA is 360 more successful.
In my opinion the only reason the 360 had any success is because Microsoft advertised and really pushed to grab the NA market. They live on popularity and image, not on games.

I think if Sony just advertises the hell out of PS4, has a decent launch lineup, and launches in the same time frame as the 360, things will go a lot differently than they did earlier this gen.

That being said, I wish for good things for both Nintendo and Sony.

PS4, because it'll be reasonably priced (no way Sony will repeat the mistake of making it $500/600) and according to recent articles, Sony is confident they'll be first to market.

Unless the 720 massively undercuts the PS4 in price, then I'll go with PS4 winning next gen. Plus the future of Halo and Gears of War are both in question. I can't see Halo 4 being as big without Bungie, and Gears is 3rd party so who knows. Sony on the other hand always has strong first party. 

Wii U. One year+ head start. Lower price... LOCK.

Should be even in the 8 gen. Same price and launch dates might make it hard for anyone to pull away.