Arrangers are just getting so good that you don't need to replace them as newer models come out. Even professionals on this board are still gigging with G1000s and PSR3000s happily. Arrangers are starting to become very mature, and need something radical to spur interest across the board in new technology.
I think it is time they combined the loop and arpeggiator functions from workstations (along with their associated sounds) with traditional arranger function, and FINALLY cater to the needs of the younger player (<30). Now THAT might get the juices (and sales figures) flowing again......
Maybe a Karma/PA1XPro fusion, or a Fantom with a built-in arranger section, or a combination MotifES/Tyros.
I'd buy one of THOSE in a flash..........
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An arranger is just a tool. What matters is what you build with it..!