I remember KM asking for a couple of years when the e473 was coming out (and I'm frankly surprised you haven't started asking when the e483 is due).
But as the DGX670 launched April of 2021,
the DGX660 launched April of 2016,
DGx650 was March-ish of 2013
640 was March-ish of 2010
630 was 2008, 620 was 2006.
You can see the times have gotten *longer*. I wouldn't expect one til at least 2025, 2026. You could keep waiting if you like.
Or, like Graham has suggested, you could play a DGX670 now.
Mark