I find the argument that Canikons have more accessories to be largely an illusion.
Consider if you will which accessories you are likely to actually buy. Most people have 2 or 3 lenses, usually the 18-55 which comes with the camera, a 70-300 or similar, maybe a ~50mm prime, maybe a 100mm macro, maybe a flashgun.
Cost of those lenses is also a factor - I got a refurbished, imported US equivalent of the Canon 400D (Rebel XTI) and then picked up a 50mm f1.8 lens for little over £50 - tis very cheap and a great little lens.
By the looks of things they dont do an equivalent for the Sony, youll have to splash out on a 50mm f1.4 lens which costs 5 times as much and in reality isnt going to be that much different.
There will be a greater variety of accessories/bigger second hand market etc.. precisely because Canon/Nikon are more popular
Having said that my next purchase is likely going to be a sigma 17-70 to replace the kit lens and I believe this is available for the Sony too.
At the moment I think the only lenses Ill require are the 50mm prime and the 17-70 as a general purpose lens - am keeping the kit lens as I have a cheap fish eye adapter for it which is fun to mess around with.