I do not see the value or advantage of getting a TF TC4.
AE copied some of the Pro 4 design features. You can get a Pro 4 that has better quality parts, it's lighter and it has more value. Does AE even include carbide diff/trust balls anymore? The Pro 4 even cheaper. AE needs to up their standard in the longevity for their parts. Since I got my Xray I have not looked back. It's so easy to drive fast.
I think belt will continue to be the future. They have more design options. With lipos coming out the weight will effecting chassis layouts. The age of molded chassis will be a thing of the past. Just my two cents.