I think the Switch marks a fundamentally new direction for Nintendo, so I expect multiple generations of Switch, rather than some completely new console with a brand new incompatible platform. That old console model is silly, and should have died 15 years ago.
I can't predict Nintendo, but if they're smart, they'll make the next generation of Switch one that actually builds on this generation, and DOESN'T kill the previous generation off by killing support - but rather leaving it around as the low end device. In which case, I can see Switch current being discounted and remaining viable on the market for some time after Switch 2, and building a far higher sales volume than people might expect. This is how smart devices outlast new generations, sometimes several new generations. And I suspect Nintendo is going to make a go at this model given the Switch's architecture and Nintendo's tendency for innovation.
So in short, can Switch sell 150 million? I'm not sure if it will, but I think it remains one of the possible outcomes. It depends on market and Nintendo's decisions on the successor and continued support for (lets call it) Switch gen 1.