This is extremely bullish. Assume Switch will sell 15m by the end of 2017; this is much more than Nintendo is projecting, but let's say so. That leaves 115m in the next four years, or an average of almost 29m per year.
That average is better than the best year Wii ever had. Only two years of DS surpassed 29m, and its best four-year period didn't average this much. And if Switch hits that number on time, even a Wii-like crash afterwards wouldn't stop them from selling millions and millions more units
So in other words, Credit Suisse is predicting Switch will be the fastest-selling and best-selling video game console of all time. This isn't impossible, but it definitely doesn't match their reasoning that "it sells like a handheld console". They don't seem to understand the import of their own prediction, which makes it less likely to be well-founded in data.
I think it means until the end of 2022, which would be 5 years. So 23m on average. Still a high prediction, basically on par with the DS.