I find it interesting that people are citing the fact that Sony could not get emulation working perfectly on the PS3, but they gave up after not trying very hard for very long. The early PS3 models didn't really do much emulating, they included the Emotion Engine and graphics synthesizer. Later PS3's emulated the EE and kept the GS, so emulation was worked on for a while. Even then, nobody knows how many people worked on compatibility fixes, but I can't see Sony plunging a ton of money into it. They'd got the PS3 through the initial launch where old games are required to balance out the lack of new games, by this point there were enough PS3 games to lessen the requirement for backwards compatibility.
Another thing to note is that CFW allowed people to emulate some PS2 games without the EE or GS chips, and the Power-based Cell is a different architecture to the MIPS-based Emotion Engine. Let's not forget that, like the PS3, the Wii U is Power-based so architecture isn't going to be the defining limitation. Using the PS3 and Sony's official attempt at BC as a comparison isn't a great idea because we don't know all the factors.
That all being said, while I think it's probably possible for the Wii U to emulate PS2 games as well as a non-BC PS3, I really don't see it happening due to the amount of work involved.
