Its safe to say as well, that in 3 years time the next generation of SKU's will be announced. XBOX may very well already have released their's. I do think that this generations game play has, in many ways, just been a revamping of the PS2 generation for the most part. Though this could be said about every new generation, I feel that specifically from PS2 to PS3, only graphics were focused upon, and gameplay remained pretty uniform.
Case in point--God of War III. Really awesome, but very similar to its previous installments. However, Metal Gear Solid 1 to MGS 2 was a huge leap in mechanics, gameplay, and level design.
Hopefully, the new sand box games will have these facets in mind rather than simply ramping up the graphics.
I couldn't disagree with this more. While mechanically there hasn't been a huge revolution, the coming of age of online play/content/communication has drastically changed the behavior in games.
To contradict the previous sentence, the biggest shift in game mechanics has been the introduction of large choice branches. Sure they are usually 'be a saint or a member of the gestapo', hit-you-over-the-head choices, but the world does react and behave in ways not possible prior to this generation. The obvious example of this being Mass Effect and its subsequent sequels. I believe the grey area will work its way into the mix as developers start getting used to the design.
And don't forget about achievements...
For me the problem of sandbox games is the developer's vanity. Whenever playing a sandbox game I get the feeling that the developer wants to make sure I see every bit of the city they created and so, like Steven said, I cannot take shortcuts or warps. Furthermore, I must trek to every corner for random points in missions because Bob the designer made this really cool statue over on 923rd St.