What do you expect the 3DS to reach?You mean like God of War, Spider-Man or Red Dead Redemption 2?
I generally agree but it takes time to build a narrative. 6 months without any big Switch games will not matter too much unless PS4/PC get some back to back GOTYs during that period.
It depends on how long Nintendo is interested in keeping the 3DS alive but I'd say some around but below 80 million units.
I don't think it's really a narrative that needs to be created, it's just that the Nintendo fanbase is limited and that once the first 3rd party AAA games come out, underperform and make it clear that the Switch is not going to get the important 3rd party games going forward (or clearer, I thought people were already aware that the Switch wasn't going to become a third party machine, but yesterdays reaction has once again showed me that I've obviously shown too much faith in the Nintendo fanbase), it'll become obvious that outside of the Nintendo fanbase, there's no reason to expect a significant influx of new people.
I simply expect the first half of next year to be the first time, where that situation is going to show, Kirby and a late port of Wolfenstein 2 are hardly going to move systems and by then fire will have died down a lot.