Many reasons.
Just the first few that spring to my head:
- Late bloomers normally have long tail ends of their lifespan. Nintendo consoles tend not to have particularly long tail. PS360; PS2 etc. all got boosted (or are being boosted) by third parties continuing to release games cross-gen, making them attractive long after the platform holder has moved on to something else. WiiU doesn't have much third-party support in the start of its life; it's not going to have any towards the end of its life.
- PS4 has shown that consumers will rush out and buy a console despite it having not many particularly noteworthy games. During the same period of WiiU's life, it was selling appallingly. I'd put this down to the fact that, quite frankly, it's an unappealing console due to its power and controller. There's nothing that can change that at this point; only price cuts can soften the blow.
- Nothing Nintendo has shown or has hinted at for WiiU has any kind of particular game-changing potential. Mario Kart is a "safe" game. Smash is a "safe" game. Next year's lineup is full of existing franchises with Splatoon thrown in, a game which may well be great but I don't think has much chance of becoming a craze. A craze is what is needed to really propel the console into the upper leagues at this point. I suppose you could say Amiibo has potential, but to me it's just their attempt at cashing in on a craze which started 3 years ago and isn't so much a craze anymore.
If Nintendo keep producing WiiU's and keep making games for it then it'll keep selling. I'm sure it'll sell at least double its LTD sales by this date. If by that definition it'll be a late bloomer to you, then sure, it certainly can be a "late bloomer". It'll have a good holiday. Smash will help. Amiibo might do something. But I don't think any of these things are going to propel WiiU to any kind of levels of success.
Edit: Oh, and I forgot the most important thing: Negative stigma. It's an uphill struggle to remove that, and WiiU has a pretty bad stigma among gamers at the moment.
