I would be curious to know what has been dropped from the PA4X. I have a 76 key PA4x. I'll keep that and buy a 61 key PA5X if there's some reason to keep the PA4X. Otherwise I'll sell it and go for a 76 key PA5X. My dealer says Korg has no idea when the 76 key version of the PA5X will ship, but my dealer already has the 61 key version in stock.