Normally the product cycle of Yamaha was 3 years, now it only is 2 years...

It can mean two things, Yamaha has started developing their next Gen Arranger and has released a keyboard containing all possible upgrades they could give the Tyros line

Or, soon there is another brand comming with a new keyboard that outperforms their T4 in almost any way possible. And now they are trying to lure customers intoo buying their product before they get a chance to realise that something better is soon comming out.