Yeah, they killed off frickin' GameBoy but waited until DS was a smash.

What if the dedicated 3ds-games end, but games on the switch get released on both (games that are probably NS first, 3ds second). Would that still count as the 3ds not being replaced?

Yes, they have said this already, nothing new here :/

It may seem like the switch should replace the 3DS, what with it being portable and all, but it would leave Nintendo without a product in that 100-200 dollar impulse buy range. This is an area where Nintendo has always done well, and it would be a bad move to leave it. This might mean supporting the 3DS longer, or it might mean a new pure handheld product.

They obviously dont want the public to the perceive that the 3ds is dying and affect sales in that regard. But yeah, obviously the NSwitch will replace the 3ds.

Not very much for HW, after revealing a new portable + home system, people wont' believe it won't replace both existing systems quite soon after its release, but letting existing users know SW support still exist, and that some will most probably exist for Xmas 2017 too, can prevent misunderstandings and help Pokémon selling all the SW it's capable of, while a clumsy timing for Switch reveal without such explanations could have damaged its sales.
This doesn't mean that 3DS could suddenly stop selling, and its XMas sales won't be by any means terrible, but I wouldn't expect Xmas HW sales as big as if Switch hadn't been revealed. Anyhow, very good SW sales and decent HW ones is all Ninty needs this Xmas, if missing HW ones are simply delayed purchases, waiting for the Switch, actually this could be a very positive situation for the new console.

Yes, it will. Specially with the hype Pokemon Go brought back, this is the most preordered game in the company's history after all. 

Good. Going to try to believe it for at least 5 minutes.

^^

At least they didn't say "It isn't replacing Wii U".   

I'd go for that Gameboy as well. But it would need $19.99 physical versions of games as well for me.