Speculation time.
I predict:
A reverb / delay kit with the same dimensions and workflow as the Heat. Let’s call it the Analog Chill.
A spin-off on that, for the guitar players, which contains only the delay part. The Analog Delay.
Then, the DigiSynth. A synth companion to the DigiTakt - paired, much like Korg’s Electribes. It’ll have eight tracks, no samples or sample playback. This will be announced no later than March, so that all who have their pre-orders on the DigiTrak can still change their mind, if they prefer the synth version.
After that, I honestly don’t know, though. Perhaps something with proper keys, for the keyboard players. But really, my crystal ball’s a bit hazy on that one.