So out of the last six weeks Switch has been down four times and the total for this period is -8.460 units. As for the last three weeks it has been down three times in a row but not by a significant amount and the numbers have improved for each week. Add to that that all this has done to the YoY difference is changing the lead from 344.490 to 336.030 and the fact that bigger titles will start to drop in a few weeks beginning with Mario Maker 2 and I'd say things look quite positive.
The next two weeks can be expected to be down year over year, because last year's E3 had lots of SSBU info that this year's E3 isn't matching with any title. A deficit of ~20k units for the next two weeks combined wouldn't be surprising. But then Super Mario Maker 2 hits and last year's baseline should be matched or exceeded, so your conclusion is correct.
The release of Dragon Quest XI S will help to make this year's September and October better than last year's even without a price cut or revision. If neither a price cut or revision happens in 2019, then I expect Switch to finish between 3.6-3.8m for the year because a new Pokémon is no match for a Pokémon remake and a new SSB; so basically weaker sales in December that will eat away at the lead that has been built priorily. With a price cut and/or revision, I expect 4m+ for the year.