Old exhaust fitting 2016 model?

Certainly looks very similar where the stainless trim runs beneath engine, depends if fixing point to subframe is also the same. If you already have the older model it's probably worth keeping (dealer won't give you any extra on the trade in anyway). Only problem is there won't be a map for that exhaust on the new engine.

 

But.... you've got a 2 year warranty to think about, if you fit a non-approved accessory you risk Triumph refusing a warranty claim. I would hang on and see what Triumph come up with on their approved accessories.
Triumph claim the new Euro4 engine has significant internal updates and obviously has more sophisticated electronics, they also say the standard exhaust is more free flowing (and lighter) so it may be that the previous Arrow slip-ons are not suitable anymore. (?)
The new SpeedIII comes with new toys and improvements, but the down side (as with most new bikes these days) is it ties you down to dealer servicing and the like..... (which is why I bought a 94R).

 

Agree with Col-c and welcome to the forum.