Yes, Switch is still selling great and the momentum is still there.
Instead of just focusing on the here and now, you should focus your attention on a little but very important detail: Switch's huge success last year hasn't made a dent on MS and Sony.
Nintendo says a lot things.
You missing point, what you or some other fan want is irrelevant, Nintendo strategy of focusing on short term is working, they dont need to focus on long term. Switch is selling great regardles PS4 and XB1, and actualy on pair with PS4 second year sales.
They dont even need to say that, from Switch launch we saw they dont showing hole years lineup on E3, of course there will be more 2018. announcements after E3 also (most of them will be 3rd party). Actually last years E3 they also said 6-9 months focus but reality was that 90% of showed games were this years games, but that dont mean they showed hole lineup in that time period, for instance games like Paladins and Fortnite are announced and released in same time period.