I'm wondering if Valve did set up shop, could there theoretically be games available on Steam that could be offered on the Wii U too (including Steam sales) and in some cases access to the same achievements (like loads of Indie titles)? With the dev's consent of course. Correct me if I'm wrong here because I know nothing about what would decide this.
So far it's all fair speculation. The only thing we know is that EA and Ubi are extremely excited about the online system. Now my worst nightmare if Nintendo would have EA as their main online partner, but I doubt that simply because Ubi wouldn't be happy about that either.
The way I see it is that publishers will likely get the chance to have their own curated shop on a unified NIN eshop. How far Nintendo is willing to let publishers take their control outside of that though, I'm not sure.
I think that these shops and games will require you to create additional publisher specific accounts, that can be coupled with your NIN profile, just like it allready works with XBL and PS3. But it's probably going to be much more direct and integrated. I'd expect publishers getting more control over patches as well.
But that would mean Nintendo would have become more forward thinking than Microsoft or Sony in terms of Online serves, and I don't think the world is ready for that.
Well given that both MS and Sony aren't exactly the be all end all entrepeneurs of online services it's definetly possible. Nintendo allready worked with an outside company for the eshop, and the criticism is taken into account as evidenced by the option to use credit cards for exact payments, and the upcoming option to shop from a browser instead of your 3DS.
We allready know that they plan for integrated video chat, so I'd expect voice and text messaging should be a given. Joining a friends game is allready possible on some games on the 3DS, so I expect this to be enhanced to true friendlist join functions as well as voip chat and chatrooms that can run outside of a gaming application.
If 3rd parties get to have their own storefronts, they'll also use their own achievements, metastatistics (cod elite), and promotions.
You could basically download apps like Elite to run directly and independently from the games. Kinda like Halo Waypoint but less clumsy.