And the current model needs to be sold for long enough to defray the development costs, and provide a nifty profit for the company, otherwise there won't BE a 'next model'!
Korg are exceptionally good at updating their OS's for new features, rather than the Yamaha way of perpetual incremental model improvements (with no upgrade path for prior models), so I would not be holding my breath for a new Korg for quite a while...
How long ago did the PA1XPro come out? That's about how long you are likely to have to wait for the NEXT Korg TOTL.
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An arranger is just a tool. What matters is what you build with it..!