It seems awfully early in the first half to be picking a winner.
As for Sony, they are holding up well with a year old model. None of the newcomers are clearly better overall, despite each having some advantages. Sony still has Zeiss and other third party optics in their corner because they opened up the lens mount. Sony have also shown that they can produce some great lenses with recent G and GM releases. We know they have a new, higher resolution, EVF coming, and no-doubt some significant sensor improvements. Will they improve weather sealing and ergonomics? Seems likely. Will they straighten out the menus... only time will tell.
Nikon has a great first release, superb EVF, with only two soft points. They are a bit behind in auto-focus, but only for certain applications. Their big Achilles heel is native lenses. If one has a stable of F-mount Nikkors, no problem. But for someone like me, with no large stable of glass, I am certainly not going to buy F-mount lenses going forward. Nikon would be smart to license the mount specifications to Zeiss and perhaps Sigma to jumpstart things. Will Nikon ever, significantly outdistance Sony in sensors? Seems unlikely since Sony is doing the fab. That's not to say that Nikon sensors might have some small advantages.
Canon is a sleeping giant. They can clearly become (have become?) number two, and might pass Sony in volume on momentum and name recognition alone. They have build great adapters for existing EF lenses. The first body isn't attractive to me, but as others have pointed out, Canon tends to lead with a trial balloon consumer-level body and then follow with the pro bodies. Hopefully the function bar will go the way of the Dodo bird, and a joystick will evolve. The real question is can they develop a high resolution sensor with class-leading DR? They haven't yet, but they have been making small improvements.
What we don't know about any of these players is the rate at which they intend to iterate going forward. We know Sony can do it every couple of years, but we don't know how fast they can go when they have completion. Canon is big... they can throw lots of money at the problem. We have no idea how quickly Nikon will iterate or introduce higher end bodies.
The second half will be interesting... I will have to go get snacks before it starts.
Glenn