I think that at this point, Nintendo is in a unique situation. the offset due to the WiiU makes this time around a bit different. I believe that nintendo can see that the next few years could be profitable with the switch, therefore it can take this opportunity to polish the next console instead of having to rush a new release. For this reason I think it could be possible the there will not be a new console from nintendo in about 3-4 years like @Wyrdness mentioned.
I think that the first quarter of next year could really tell us about the demand for the switch. If it somehow manages to keep pace with what it did in 2020, then I see that as a great sign that it will be able to be profitable for at least 4 years. These are the first three months of 2020: