In my opinion the:

PS4 will have 150 million sellers.

Xbox one will have 100 million sellers.

Wii U will have 18 million sellers

3DS will have 55 million sellers.

PS Vita will have 6 million sellers.

Previous Gen consoles had:

PS3: 227 million sellers

X360: 221 million sellers

Wii: 156 million sellers

Ds: 139 million sellers

PSP:  56 million sellers

Edit: Could a mod change this into sales discussion

How much did past consoles have?

Yeah, for PS4 is going to be really easy to convert almost every bit title a million seller, Xbox One situation is pretty different because they are struggling trying to convert every big title on a million seller that fast, and that situation happens on smaller multiplatforms like Shadow Of Mordor, so 100 is pretty possible... Then, Wii U have the possibility to reach 30 million sellers easily by one reason, legs... As we saw in 2013, games like NSLU and Wii Party U finished as million sellers, and games like DKC:TF and Pikmin 3 which had slow FW sales, are going to finish being Million sellers too, finally, 3DS can finish with over 65 million sellers easily... Vita with those 6 are ok!

Why so few? PS3 got well over 200.

You have to consider though that the PS3 had a lot of third party games based on movies and really bad games which sold over 1 million. I don't see that happening this generation. Games such as the Lego series will not be million sellers this generation.

Fixed

Thread moved.

PS4: ~250 (currently at 26)
XB1: ~160 (currently at 16)

My estimates for PS4 and XB1.

Is last gen also your opinion? Because it was actually like this:

Wii 101.23 mill
x360 84 mill
PS3 82.3 mill

(source: http://en.wikipedia.org/wiki/List_of_million-selling_game_consoles)

PS3 never sold 227, not even PS2 (the best selling console ever) with its 155+ million.

Why should PS4 be better than PS3? For what? It has reboots, sequels, PC ports, games that already exist on last gen, games with cut content to be sold separately.