The word marketing has been used in this thread so many times. But the ones using the word have not stated any sound marketing reasons why Yamaha is not producing a 76 key arranger.

There has been no evidence that there is not a substantial market for 76 keys or that a 76 key would turn away those who have used 61. In fact there has been overwhelming evidence to the contrary.

If the customers who would buy the next T3 found out it was 76 keys does any one really think they would not by the T3 because it is 76 keys? They are buying it for Yamaha sounds, styles and OS. Where or who are they going to run to. If the sounds, styles and OS are the superior Yamaha quality that people are accustomed to and expect, if the keyboard is 76 keys it is not going to be a deal breaker. The fact is Yamaha is a market leader and they like Yamaha so who are they going to run to. The T2 has a funny look but did that hurt the sales? No. Yamaha took a big risk with the look of the T2. But Yamaha new that since their sounds, styles and OS are superior they could take that risk because even if people do not like the looks, the sounds, styles and OS would compel people to want to buy the T2.

Now with a 76 key T3, it is not a risk to Yamaha because it is not giving their customers any thing less. It has no effect on the usability of the keyboard from a 61er prospective.
As most of us can agree, the only effect a 76 key arranger could have on Yamaha is to bring them more profit. It can not hurt Yamaha it can only hurt their competition.