Historically, Nintendo has announced things with that kind of lead time, but as of late, Nintendo has kept announcements much closer to the launch date. The Switch from announcement to launch ( Oct 20-March 3) is 134 days. Today, January 11th, we are 137 days away from Memorial Day (May 27), which is the unofficial start to Summer. The real start, June 21st, is a month after that.
My point is, things are way more open. Nintendo can announce and release the thing very quickly if they want to, and I find that much more likely than the drawn out reveals over 18 months that the Wii and Wii U got.
If you count those investor mentions, then sure, the Switch was announced quite a long time before. In my mind, those were so vague, that calling it an announcement was a stretch.
I guess in my mind, I look at the fact that nearly every tech and media company has been moving toward announcing products closer and closer to the release. You go all in on a big marketing plan, rather than a drawn out one for over a year. I am expecting a similar schedule for Nintendo with this new system.
Of course, Nintendo is still so successful with the Switch as is, I can see them feeling significant freedom in making an announcement whenever they want. As you mentioned, there aren’t antsy investors to please right now.