It's true the PS4 has a Pro model, which could sell to current PS4 owners, but the Switch offers a different kind of sales advantage to Nintendo.
Consider if you will my nephews. They share between them an Xbox 360, a PS3, and a PS4. Then they each have a Switch. Households where consoles are shared between kids are more likely to have multiple Switches than they are multiple PS4s due to the Switch's portable nature.
Yes, it's true that Switch's mobility provides incentive to own more than one but I will also say that its function as a console provides incentive not to own more than one. A Switch can be played by more than one person, a 3DS cannot.
Don't worry, Switch will get its redesign and massively inflate the sales numbers soon enough.
Yeah, very likely.