Nintendo has a proven track record of iterating on hardware. E.g. Gameboy Pocket, Gameboy Color, Gameboy Light, DS Lite, New Nintendo 3DS, Nintendo 2DS... I could go on, but I'll just rest my case.
Reggie is just saying that so the current Switches keep on selling. He's a business man. He literally has shares in the company. He wants people to continue buying the Switch (which is fine, it's a good piece of hardware). BUT THERE WILL BE A NEW ITERATION OF THE SWITCH!!! GUARANTEED!
The launch version (the one I've got) is a good piece of hardware. If you buy it, I'm sure you'll be happy with it. Just be mindful that there'll be a new Switch sometime. It may take a few months, it may take a year or two. I can guarantee you there will be a new Switch.