People need to realize that UE4 engine comprises of two main components, the Tool chain and the rendering pipeline. While the tool chain can be used on WiiU development mainly because it runs on computers and not the console, the rendering engine can't.
The UE4 rendering engine simply needs more powerful hardware to achieve the level of visuals which epic have set out to achieve, they’re after all a graphics engine middleware company.
All you need do is look at the engine running on PC, it requires a GTX680, which is a top of the line single core GPU running at 3.1 TF, while it has been customized to run on the PS4, which it in its self is reaches 1.84TF, the WiiU simply has no hope of running the same rendering engine considering that the WiiU only reaches about 400GF.
So much of the UE4 would have to be cut out to make the rendering engine work on the WiiU and then the best you'll get would be more equivalent to what the UE3 visually already produces versus what UE4 looks like on more significantly powerful hardware.
Frankly it's the law of diminishing returns on the WiiU's constrained hardware, I mean sure Epic could port the UE4 engine to the WiiU and have it look maybe marginally better than UE3 on the WiiU, but would this make business sense when you already have the UE3? I think not, and for this reason alone Epic have made the business decision to set the base level of UE4 on the PS4, Microsoft next console and mid-top end GPUs, meaning that lower specced machines like the PS3, 360, and WiiU will only get UE3 and not UE4.
Also I find the OP tittle funny, basically saying if the PS4 gets it why not the WiiU. Either his elevating the WiiU to the PS4 level, or brigining down the PS4 to WiiU level. But let’s face it; the largest dividing gap between the PS4 and WiiU is the sheer amount of ram. Assuming that PS4 reserves 1GB to OS, that gives the PS4 7GB of ram for a game to work on versus just 1GB on the WiiU.
Let’s put this into perspective so people understand the significance of this. The PS3 has just 512MB of ram, the 360 has 512MB + 10MB EDram, we now subtract the OS and PS3 comes down to 456MB (OS about 56MB ), 360 comes down two 490MB (512+10 minus 32MB OS). The 360 has 34MB extra for developers and this resulted in some multiplat games having slightly higher/sharper resolution textures on 360 versions of the same game, sites like Digital foundry and lens of truth did side by sides showing this. Most often than not the 360 had the slight advantage cuz of the extra ram, now imagine if we bump up the 34Mb difference to 7GB. We would be looking at essentially two different games which play the same.
I'm sorry to say but Nintendo fans need to accept that the WiiU has PS3/360 level hardware, it will not come close to matching Sony and Microsoft new consoles on the visual department. I understand that Nintendo fans aren't happy, and that they would like to think that the WiiU somehow can match the PS4 and Microsoft new console, I don't blame them after all Nintendo basically came out saying that the WiiU would be a power machine, that they'll have the definitive versions of call of duty and what not, and how they will be going after us the core gamer, but realistically that was a dream which was not realized on their hardware. It’s true that the WiiU is more powerful than the Wii, but Nintendo cannot live in the bubble they do, they have direct competition and need to zoom out to see the greater field.
My 2 cents.
Rant//
I'm a little annoyed at Nintendo fans in general, I may be generalizing a little, but the vocal minority will always make the rest look bad.
I always hear from Nintendo fans say how it's all about gameplay, how it's it's gameplay > graphics with no exception and this is why certain Wii games are supposedly better than PS3, 360 games making them games of the foreva, but then when Nintendo have the possibility of realizing a graphics capable machine all of a sudden the fans are ecstatic that a Nintendo machine can finally compete against other consoles, and how the bird tech demo and zelda tech demo where the best visuals ever. Some even saying that Sony and Microsoft could not make a more powerful console than the WiiU because of diminishing returns and how it would cost way way to much, saying it as if it where a known fact, and yet here we are with the PS4 with it's specs revealed and all of a sudden most Wii fans are defaulting back to their gameplay over graphics mantra with only the ultra hardcore Nintendo defending the WiiU specs at all cost, despite what is known. With time these people too will default back to the same gameplay over graphics mantra.
To me games are a interactive visual medium, both Graphics and Gameplay are important, and we live in a time where both can be achieved. Just think about the core of what we do with games, we constantly look at them as we receive visual input and we are constantly feeding input into the games through the controller, and because these are the two main things all of us do when playing games, then it stands to reason that both should be the best they can be. People need to remember that we are visual creatures; to say otherwise is to be disingenuous to your biology.
I understand fans will be fans, but truth and logic needs to prevail especially when facing all the available data, this spawns discussions rather than troll threads or derailed threads.
//Rant