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.
But probably stronger than either of those on it's own. So it just needs another big release during that time to get similar results to last year.
Speaking of which, how do the Mario & Sonic at the Olympic games series fare in Japan? Could they bring in at least some of the needed boost to equal last year's sales? How about Luigi's Mansion?
I understand neither of those two is as big as a Pokemon or Smash title, but couldn't they reach a similar effect, when taken together? Especially since I expect the baseline to be somewhat higher from the game releases in late summer.
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454