That's bollocks.
Project Reality was announced in
August 1993, a whopping THREE years before the N64's eventual release (recall that it was originally due to launch in 1995 before being heavily delayed).
Project Dolphin was announced in
May 1999, 2 years and 4 months before the Gamecube's Japanese release.
The Nintendo Revolution was announced at
E3 2004, and shown off in physical form (with the Virtual Console announced) the following year at E3 2005; 2 years and 6 months prior to the Wii's release!
Wii U was announced on
April 25, 2011 and formally unveiled at E3 2011; 1 year and 6 months prior to its eventual release.
NX was announced in
March 2015, formally unveiled in September 2016 and released in March 2017, 2 years following its initial announcement.
To take some non-Nintendo answers to this question into account as well...
I could go on, but you get the idea.
Nintendo
always announce their next console prior to its formal reveal. That hasn't happened yet, and that means that any release before March 2023 is now incredibly unlikely as it wouldn't give enough lead-time before release. November 2023 is currently the most likely date (which also conviniently coincides with the end of Mario Kart 8 DX DLC support too).