Sir Bob,
It is very unlikely that yamaha will re-introduce such keys in that price segment. This year I got the chance to visit a lot of stores where both I455 and I500 were available, brand new piece. And keys were exact similar, no difference. So I don't think I400 will bring some new changes as it already looks like a tuned down version of I500, or the successor to I425. Still I would try it out in stores, though I believe it won't be coming to my city before second quarter of 2020..
Sir Michael,
I believe, with this introduction Yamaha is re enforcing localised keyboards in Indian market, and might cut short, or stop the sale of global models like E463, EW410. After I400, the EW4xx or its successor might won't be seen in India, as its demand is already very meagre.
One important thing to note, the price difference between these two keyboards (I400 and I500) is of approx 70$, so already Yamaha has launched similar keyboards in a similar price bracket.