I think discussions like this are largely elementary.
Nintendo's already made the decision about the Switch successor and it's probably been made 1, even 2 years ago at this point. I doubt they are looking at sales trends week to week or month to month even right now and factoring that into the equation all that much.
Also again, not sure why this has to be pointed out like 50 times, but Nintendo themselves had no intention of letting the Game Boy product cycle go on that long. They were committed to replace the Game Boy by 1995/96 with the successor (Project: Atlantis) ... the company making the system just could not give Nintendo what they promised (on battery life + performance + cost + size), so Nintendo was unable to release it.
It's probably a large part of the reason Virtual Boy got rushed out onto the market (Atlantis being behind schedule and N64 also failing to meet Yamauchi's holiday 1995 target date).







