If I'm understanding the question, it's "What things that are
perfectly reasonable extrapolations will not turn out like that, or
what things will we be totally blindsided by?"

For example, the various sci-fi books where they have a bulky radio to
contact the ship in orbit... and considering that the NSA has sats
that intercept cell phones, a starship should be able to work with a
smartphone held by a crew member.

If that's the case, Traveller is chock-full of AF (grin)

I think the biggest thing that is missing from Traveller, in the same
way no Lensman has a smart phone, is Makers of various sorts.
I keep looking at the game Eclipse Phase, and playing with the idea of
stealing from it for details of TL14+ worlds.
The campaign I was running, I mis-remembered Efate as being TL15
rather than 13, and rather than retconning I just went with it... and
none of the players (most new to Traveller) really pushed on buying
super-high-tech stuff or asking/looking for the things that would have
lead to me digging out the EP book.
(Silly players... missed a big chance there...Thank Goodness)

I think body modification is going to be bigger than Traveller makes
it out to be, but smaller than some views of the future push. Most
people aren't going to hack themselves into walking monstrosities, but
implanted computing will probably happen so long as it's cosmetically
neutral. I can see the Imperium having an emergency medical dispenser
implanted along with the computer run it, do translations, VR
training, and enough comms to work as an emergency beacon. The
implanting would be the equivalent of getting tons of vaccinations
during basic that we have now.