Yeah, new stuff is lighter, but they continue (continued? Unsure of this year) to sell the TLT 6 as the speedfit/speedfit pro with very minor changes. I guess the question would be how good of a deal, as I’ve seen the speedfits going for pretty cheap.
I learned in tlt 5s and have found them totally up to the task of light duty touring. Simple, light (especially the carbons). Very narrow. Im no expert and I'm sure boots have gotten far better but I think a good deal on tlt 5s is still a good deal.
If you already have TLT5s I don't see an urgent reason to replace them with a current boot. If a pair fell into your lap you should use them but know that they are difficult to punch for width at the ball of the foot because of the joint that they have. That joint is also a failure point and many have died prematurely from cracking due to the flex in the toe.