Nintendo knows that the 3DS will fade as Nintendo Switch grows, and they need to fill that lower price entry point to expand the platform significantly.
People hoping for some powered up SKU that has a bunch of games the original Nintendo Switch cannot run have not paid attention to Nintendo’s history with said revisions. Anytime Nintendo has made such SKUs (i.e. DSi and New 3DS) they have allowed developers to make games for them that do not run on the original models, and the amount of total software that actually forgoes the existing user base has been very very very few titles. It just does not make sense for the financial side of things for developers to cater a portion of the install base rather than the whole install base.
Will Nintendo make Nintendo Switch models with newer and better SOCs? Probably so, but the performance benefit will be marginal to non existent at best, as the focus will be to reduce cost of the total cost of materials (i.e. a 7nm SOC would allow them to put a smaller battery, reduce the entire chassis size, and remove the active cooling).
Nintendo is not focused on upgrading resolution of their consoles. They are still selling a 240p handheld console in 2018 at reduced costs with a very healthy profit margin on hardware and will continue that focus in the future.
In 2023, the Nintendo Switch will still have a 720p screen and Nintendo will be happy with the low cost and high profit margin and will have multiple SKUs.
Nintendo's focus is it leverage its software library to sell its hardware, and to reduce costs of hardware while addressing a wider audience. Focusing on CPU and GPU power and splitting their user base is not where they will expand and Nintendo knows this.