I just describe how industrial production works.
Take the pattern I described, and compare it with ascent and decline of ANY musical instrument Empire.
New products are not determined by NAMM approaching.
Otherwise, you could make FOUR NAMMs a year, so technology would advance at twice the speed and you would sell double the keyboards...
You don't get new products from "wanting" them or from "needding to put them out", or from "a cycle being ended". The Minimoog cycle was ending, time was ripe for a polysynth, abd Moog couldn't produce and sell one, and the company went belly up. You get new products if you CAN make them.
New products are determined by the money you put into research and machine tools.
And Korg obviously hasn't done much research and investment lately.
Its recent products are patently the fruit of salesmen brainstorming (uhm... "brain" is maybe an overstatement), trying to make a new thingamajig out of old ideas.
Not a single engineer was involved in the process, or the m50-61

If Korg had in store "something" (anything) better than "micro-keys for pea-brained DJs" they would have used it in their struggle against successful newcomers like Clavia, not to mention Yamaha (come on: is a "red stage piano" with 12 presets and no splits a serious answer to the nord stage? even to the nord electro? Is it an answer to the roland v-piano?).
Korg totally missed the "analogue revival" boat, and finally, after the mopho, the prophet08, the plethora of small 300 us$ analogue monosynths (dopefer etc)... they finally dig into their history, think of the ms-20... and get into the market... with the monotron?!?
Any kid can buy a used darkenergy for 200 usd and solo on a 5-octaves keyboard with velocity and aftertouch control. If he is in the money, he can spend 500 and get a Mopho... An Korg replies with the Stylophone-on-Ritalin?!?
Is THAT the technology they have in store for announcing a groundbreaking keyboard at the NAMM?
You say that "it's 3 years since they did anything, so they HAVE to do something". Wrong. A serious recession happened. We could lose 10 years in serious technologic advancement. Look what happened between mid 70s [analogue peak] and late 80s [Korg m1]. If japan hadn't somehow profited from the US crisis, we would have missed even the only true event of those years, the DX7.
This time, Japan is not richer than US.
And the Chinese can't yet build decent instruments. Wake me when CME will be able to provide user manuals and technical support for their products.

Korg took 12 years to overcome the production problems (=lack of capital problems) of the Oasys. I am afraid that that miscalculated effort drained them of any energy for some time.
The M3 was supposed to be the "money making", "mass-market" offspring of the Oasys project, the way of financing the NEXT project by monetizing the Oasys technology, and it flunked.
It could take 10 years to recover from such a miscalculation, in the current economic environment.
Frankly, before Korg releases something serious, I expect news about some kind of money infusion or partnership.
This, not "M4", could be the "great surprise".