Handhelds are not an accurate comparison. Switch is not a handheld exclusively. No Nintendo home console has gone longer than 6 years. Nintendo won't risk releasing the successor later than 2023 and getting that behind in terms of what's being done in the industry. The Switch is going to start to feel archaic compared to what developers are doing on PS5/X4 by 2023, Nintendo will feel like they're in the dark ages if they push the Switch further than that and it will hurt their reputation.
Switch is neither a home console or handheld exclusively, but that's a positive thing. It draws developer support from multiple avenues and more games mean more sales and more potential for a longer lifecycle.
Given that the industry trend is going towards streaming and the idea to play console games anytime, anywhere... don't you realize who has the best product on the market? It's Nintendo, because their solution doesn't require an internet connection and doesn't have to deal with input lag.
If you are talking about graphics, Switch launched with weaker specs than consoles released in 2013 and has so far only gotten a single-digit percentage of AAA multiplatform games that were released since March 2017. The market response to that has been a clear "it doesn't matter", so unless some company puts out a hybrid console to compete with Switch, Nintendo will remain the king of a hill that is all theirs while having a significant presence in the home console market and a significant advantage in the anytime, anywhere buzz.