I respect Nintendo enough to trust them to make the right decision, design wise.
If they do a cartoony game, I would be okay with that; I am sure they can make it work.

I don't think it would work. For starters, Metroid games have always gone for a more realistic approach, so it would be a big departure from the series, but there's also the fact that the Prime arc have a distinct dark tone in its story that doesn't seem well suited for cartoon graphics like those of Wind Waker.

That said, with the right art direction, some other kind of cell-shaded graphics could actually work, like it did for the Borderland games.

*Edit* PS: Your english is fine, don't worry too much about it.

I think I could live with something on Borderlands style although I prefer something on the realistic side this time or with traces of Dishonored. I wonder how would be the reception for that.

edit: Your English is better than mine, OP. It does not mean much, though. xD

I was around to see the shit storm that was the Wind Waker and the negative impact it had on the release and hype of the game (despite some of you younger people who were kids and didn't know about it) so I wouldn't even want to THINK about the same thing happening to MP4. Given the type of game Metroid Prime is, it would be a clusterfuck to end all clusterfucks and Nintendo doesn't need that type of press right now.

What if Samus has a form of transportation in Prime 4 that allows you to move from point A to point B more quickly? If they are going to take anything from the Wind Waker, why not the method of transportation? It does not have to be a boat per se. The planet could be far more expansive this time around. The last 3D Metroid was on the Wii.
Nintendo can do much more than prettier graphics. They can make the planet larger too.

The idea of flying through space and going to other planets would be good in theory, however, it would be eerily to similar to No Man's Sky, and that game was well - lackluster. They can instead focus on a really in-depth, detailed, expansive planet to explore.

Bring it on people said Zelda should be realistic in graphical approach and not cel-shaded that notion got shot down, they said Metroid wouldn't work in first person that also got shot down so if they go for a radical approach then lets go.

If Prime 4 went full on Wind Waker, then talk about a shot in the foot.

I think Other M should be the awnser in terms of artstyle. Detailed and yet verycolourfull and unrealistic. Sakamoto in an interview said he was inspired by Dario Argento horror movies like Suspiria.

I'm not a fan of Other M but I think the game looked fantastic, even cosiderating the hardware limits of the Wii

I totally forgot about Xenoblade, then I suppose they'll continue with realistic graphics for MP4.

Absolutely not. It would be equivalent to Nintendo trying a hyper realistic art style with a Mario platformer. Just wouldn't fit (and no, New Donk City isn't a "realistic" art style just because it has more realistic humans before anyone brings that up). And I'm very lenient on art styles in most cases for Nintendo games, but Mario and Metroid are two franchises that pretty much need to stay locked into a certain style.