I think the Wii U will start selling more by the end of this year. I think when this gen is over the Will U will sell around 40-60 million. The PS4 probably going to sell the most. XBOX1 will catch up and probably pass the ps4 if HALO comes out for it soon.

The Xbox brand is irrelevant outside of English speaking countries. In Europe, the PS4 will have a large advantage, but I do not see an advantage similar to the PS2, because of high taxes and economic crisis, Furthermore the Xbox brand is very popular in the UK, and this will help balance the sales in Europe.
In the USA I see a hard battle, with perhaps a slight edge to Sony. Japan seems irrelevant, maybe the PS4 sales are the same as the PS3 sales, it can also sell less if Sony leaves the PS4 as main console for less years or if the economic crisis worsens.
I might think than Sony with a lead 25-35 millions, especially because of Europe. But let's see how the market will behave in the economic crisis and, how will be the long-term sales in the United States.

Too early to tell

So PS4 will sell less than the PSP?

I do not think the PS4 is going to crack past 100M and the Gen will probably not be as long as we are thinking.

Id go with something more like this:
90M = PS4
50M = X1
20M = WiiU

Not at all.

While the PS4 will remain strong, exactly for the same reason as the PS2, the Xbox One is a serious contender to the PS4 unlike the Xbox which nobody wanted.

As for Nintendo, Gamecube was one of the best console out there, not only more powerful and beautiful than the PS2 but also had the best Good Exclusives/Releases ratio with lots of crazy third-party exclusives.
The Wii U is already outdated hardware, no third party or legacy game want it, so it's already and will be struggling but for good reasons this time.

It's possible that MS doesn't like where this gen is heading and will attempt to force a new generation 2 years from now.

MS just seems like a company that's unwilling to stick with a product if it's not an instant success.

If we are talking about the order of the console sales, then yes! If we are talking about the console sales themselves, then not really! The only console which will do around the same as its 6th gen counterpart is the WiiU!

It makes the Nintendo fan in me cringe, but I don't think the PS2 will ever be bested in terms of home console sales.

I don't think so, Xbox One will sell too much to be comparable to the Wii U.