Donny,
For me buying a different keyboard is just that - it's different. For the last 10 years I have played 5 to 6 Senior Venue gigs weekly playing just about the same 100 songs because that is what they ask for and enjoy. It reminds me a lot when I was traveling with various big bands. Most of them had a book of about 100 songs that we played night after night. Why, because that is what the dancers came to hear.
Anyway, it is nice to have a little different sound to those same old songs. Regarding the T5 replacement, it will have to be very very good and much different from the T4 I now have. Frankly, I have been very happy with my Ketron SD7 and so has my audiences.
Deane