I would not use a tablet for gaming so it wouldn't deter me from getting a Switch. I wouldn't be able to get the games that I normally like on a tablet so it wouldn't do my any good. I can see using the tablet for reading, especially if I am traveling or in the process of moving. But I don't see myself using it for gaming.
As far as the Switch goes, I see it as a console. You just have the benefit of taking the console on the go, if you wish to do that.
I think Nintendo fans will be more likely to get the Nintendo Switch when it is released, or the following few weeks after it is released.
But, I think the Nintendo Switch will not sell as many consoles as the Wii's first few months of released because the general public now has more devices to game on, and more games to play on devices like tablets and other consoles and PC.
The general public who have a tablet, or can now afford higher quality $50 tablets from a better brand like the Nook 7 and Amazon Fire $50 tablet may wait longer before seriously thinking about getting the Switch.
The general public may not consider getting the Switch until there are must-have games they want to play like Zelda or Mario Kart, or the game has an important purpose in their life like Wii sports which helps motivate gamers to exercise. I think more tablet users are happy with playing game titles like Grand Theft Auto 3, Final Fantasy 3, Minecraft, Sonic, Hearthstone, etc which are available on tablets, and can run on cheaper tablets which have gotten a lot faster over the years.
Buying a wireless Bluetooth mobile controllers for $30 or less also give tablet gamers a similar gaming experience to a handheld, game consoles and PC/laptop which uses a controller for gaming.