To me this thing is already dead in the water. Reasons why:
1) The console will be underpowered, thus ports will always be the weakest performance-wise. Showing a 5yo game at the first presentation(Skyrim) is so bad it's hilarious again. Which will also lead to
Perspective is everything.
The ports will be the most amazing handheld ports of games that cannot be played elsewhere on a handheld.
PS4 and XBO are weak performance-wise compared to a PC.
Switch is not weak and will not be weak. It uses the most cutting edge mobile tech there is.
2) Third-party support lasting about as long for the WiiU, meaning a very short time. If the leaks are true about it being roughly 3/4 of a X1 performance-wise then there will simply be a technical barrier very soon. And even if they were almost equal, most people still already have a PC/PS4/X1 and play with their friends there, so they are not going to get the inferior version just because. We've seen it with the failed WiiU ports of ME3 and Watch Dogs.
Being able to play with your friends locally and online, maybe at the same time, is something PS4 and XBO cannot boast. Trying to tell the future based on the past is a fools errand. There is no trend. Each console release is a clean slate and has no impact on the past/future. Wii success was unpredictable. Wii U failure was equally so. The truth is we cannot know until we know.
3) Realistically there won't be a GTA or FIFA/CoD (for more than 1-2 years/with full functionality) on the console, thus basically eliminating it already for casuals.
If so, it won't be due to technical limitations. GTA V is a last-gen game and could easily run on the Switch. GTA VI isn't coming for a long time. The "casuals" you list are only a subset of casuals. There is Madden, and Nintendo has their own fair bit of casuals who don't play PS4 or XBO.
4) The whole "play on the go" thing is nothing but a gimmick and a hilariously bad one at that, incase the rumors of 3h battery life are true. Nobody meets up at a basketball court just to then play virtual basketball instead. And nobody (as in not anywhere near enough people for it to be relevant) are going to play a hardcore game on a 30min bus ride.
Breath of the Wild is a hardcore game. A lot of people, more than enough to be relevant will be playing it on the go. Portability is not a gimmick. It is a very desirable feature for games. Don't believe me. Look at mobile. Mobile cannot boast Skyrim-like games, but Switch can, making it completely unique in the marketplace. Learn the difference between a "gimmick" and a feature.
5) Price is probably 300-350€ while at the same time you will probably be able to get a nice PS4slim bundle for 250-300€ already.
Can I play a PS4 slim on the go? No, I didn't think so. Can I play Nintendo games on it? No, I didn't think so. What good is a PS4 slim without these key features in my life?
I believe the only people buying this console will be the same people who bought the WiiU + some handheld outliers. Meaning it will be the usual "play-nintendo-firstparty-games-and-nothing-else"-machine.
"handheld outliers"? You mean like the 60+ million 3DS systems sold? Those "handheld outliers"?
In all honesty, I plan on playing exclusively on the Switch. I hope the Playstation Japanese devs like NIS, Atlus, etc. bring their games to Switch because I will buy them up. If Switch gets a port from the other consoles, the Switch version will be my main and preferred version (if I get them on the other consoles at all).
The Nintendo Switch is my future main console. As a parent and someone with a busy schedule, it is the perfect machine to lay in bed or anywhere in my home or during my lunch break at work.