A few things:
Far Cry 3 on PC isn't representative of next generation gaming, in design anyway. Fact of the matter is even these games that look gorgeous on PC are, for most part, built to be scaled to current generation platforms. It introduces design and scale limitations to the core of the project. After all, if you make your game too reliant on high end PC hardware, you may not be able to port it to the 360/PS3 at all. What we tend to see with these titles are games that can safely run and function on the 360 and PS3, and for PC we see a second coat of paint to spruce up the presentation. Sometimes that second coat of paint can be trivial, other times dramatic. But end of the day, the game itself will be exactly the same.
Now, a game built to fully take advantage of computing power of high end PC hardware? That could be something else entirely. We haven't really seen many, any of these games (Total War series probably pushes the bar higher than any other game), and won't until the next generation platforms come along. Building projects for high end hardware means more than flashy visuals. It means great scene complexity and density, arguably richer and more dynamic world interactivity, and other goodies that require complex computing power.
Take, for example, procedural destruction. We've seen some games this generation toy with the idea (eg: Red Faction: Guerilla), but the processing requirements are simply too high. Next generation it will be less of a problem, and we may see more games adopt procedural destruction and other gimmicks into design, doing so in ways that were impossible on current generation platforms either because of raw computing limitations, or RAM bottlenecks.
Where the Wii U will sit in all of this will depend on the hardware. I think sometimes people look for a cut-and-dry answer to the porting question, as if we can say "okay the Wii U is a 6/10 and the 360/PS3 are a 3/10 and the PS4/720 are an 8/10, and 6 is closer to 8 than 3 is so that means we'll get ports", but it just isn't that simple. Difficulty of porting will depend on the complexity of the games, the engines running those games, and what developers are willing to sacrifice to get the games running on weaker hardware. Some games from this generation were, with appropriate scaling, possible on the Wii. Like the Call of Duty series. Other games most definitely were not, not unless the devs took a hatchet to the design and started sacrificing big things to scale the game to weaker hardware. Assuming the engine could even run on the platform at all.
I do think we'll see titles next generation that could be scaled down to the Wii U. How far they'll need to scale will vary, but I think many games will be 'possible'. Whether or not publishers see it as worthwhile is another matter entirely. But I'm also confident we'll see plenty of games that, for whatever reasons, would be too difficult and frustrating to scale down to the Wii U, much like the Wii, where from a developer point of view too many components of the design and presentation would need to be sacrificed.
But, you know, this is all just speculation. Fact of the matter is nobody here is able to truly predict how next generation will play out, where the capabilities of the Wii U will sit relative to the other next generation systems, and what difficulties developers will have with the platform relative to processing requirements of their new games. We'll just have to wait and see.