The Fusion idea would mean selling a lot of combined hardware, increasing the home console numbers (maybe even bundling the two machines with one or two free games?). The handheld part would be difficult, but as long as they make Pokemon, they can at least match the 3DS sales.

Who cares that Wii was more powerful than PS2/Xbox? That aspect had absolutely no bearing on the success of Wii.

Their really isn't this huge difference between handheld and console gamers, at least when it comes to Nintendo. Look at all the big selling titles on 3DS, the majority of them are popular games that originated on consoles with the exception of Pokemon. Certain games have more success on one or the other, something like Animal Crossing is popular on both but clearly more so on handhelds just as a game like 3D Zelda is probably more suited towards consoles.

Gameboy pre-Pokemon had mostly sequels/spinoffs to popular NES games, Tetris was the only game that sold vastly better on the handheld. Big  games on GBC/GBA, outside of Pokemon were mostly sequels/spinoffs/ports to popular NES/SNES games.

PSP was mostly sequels/spinoffs/ports of popular home console games. Monster Hunter was the only one that sold a lot better on handhelds.

DS was the only handheld that has had a large selection of handheld specific titles and many of those games have seen huge declines recently. Brain Age is practically dead, Nintendogs had a nearly 20 million decline from the DS version.

Pokemon and Monster Hunter are the only really big titles are still relevant with a much bigger handled presence. Even so, Monster Hunter is still fairly popular on consoles and Pokémon never saw a mainline console title but they have had a bunch of successful spinoffs, so no reason to believe a mainline title wouldn't be successful as well.

I think it can, they learned from their mistakes this gen and hopefully don't mess up next time

It very much does matter that the Wii was more powerful than the Xbox and PS2.  But now imagine if the Wii had been half the power of the Xbox?  Good lord it would have caused rioting.  A "modest" upgrade the Wii U - say  75% increase - would result in the Wii U's successor being very noticeably weaker than the PS4 and Xbox One with virtually no noticeable visual upgrade of any kind over the WiI U and the thing would be a joke of a joke compared to the next Xbox and Playstation offerings.  And I was simply making the point that there has never been a console weaker than the previous gens offerings.  Ever.  And if there was such a platform, the ammount of backlash, insults, and bad press would destroy it.  This is the age of connectivity; the news sites and even developers and publishers out there would absolutely rip them to shreds to the point where most people wouldn't even touch the thing.  Public perception is huge and this would ruin Nintendo's image for good.  Remember all crapstorm of 2013?  All the insults and borderline slander?  Multiply that times 10, I absolutely guarantee you. 

I don't know.
I am hoping better, but Nintendo really needs to have an interesting launch game to show why the next hardware is awesome.

1. NES had Super Mario Bros.
2. SNES had Super Mario World
3. GB had Tetris
4. GB Pocket had Pokemon
5. N64 had Mario 64.
6. DS had Brain Age
7. Wii had Wii Sports

If Wii was half the power of the Xbox, it still would have gotten all of the Nintendo games and kid/family/casual friendly 3rd party software. Literally nothing would have changed, it was already mocked for being weak, making it weaker would have just seen the same thing.

When will people realize that the PS/XB audience is not the same as Nintendo's. Nintendo devices have always sold based on their exclusives, even back in the NES/SNES days when Nintendo did have strong 3rd party support, it was exclusives that sold the consoles. Take away Nintendo's 1st/2nd party titles and make Final Fantasy/Mega Man/Castlevania/Dragon Quest/etc multiplats and NES/SNES dominance comes to a screeching halt.

Nintendo consoles also don't sell based on power. Did NES dominate because it was a graphical beast? No, it dominated because it had 100's of  games not playable on other devices. Did SNES beat Genesis because of power? No, it beat it because it had the more popular exclusives. N64 was more powerful than PS1 yet it sold 70 million less. Gamecube was more powerful than PS2 yet sold 135 million less. Wii was way less powerful than PS3/360 yet outsold both.

Nintendo consoles sell based on the software, not the power. Wii U isn't selling poorly because of its power, it's selling poorly because it has an awful software output, costs too much for what it offers, and has horrible advertising/marketing.

A low-cost console with high exclusive software output is what Nintendo needs, being as powerful as the competition doesn't really help them, it just gives them a slightly higher chance of recieving multiplats which have never been a huge contributor for Nintendo's hardware sales.

What a strange topic. How should I know? I have no idea what those systems will be like.

I could make a guess based on this generation sales, but when has that worked? Based on that, nobody would have expected the Gamecube's successor to sell 100M+ or the XBox successor and PS3 successor to sell the same amount.

I don't want to look pessimist, but I'm not sure 3DS is going to reach these numbers.   I believe the next Nintendo console will do better in the market than the WiiU is doing while their next handheld will do a little worse.

3DS+Vita is on track to sell that much, u can't exclude one device just because it's not selling well

I think dedicated handhelds will continue to decline into the 50-55 million range next gen (maybe even less)

Nintendo's next console will sell about the same as Wii U, but I think it will be more profitable, being based off the handheld chipset, so it will be cheap and profitable from day 1.