The MT Campaign did indeed introduce a few TL16 worlds. If the Final War wasn't so final, You could've speculated that the 3I would have been a true TL16 culture by about 1140 or so.
One thing you need to look at about TL16: it isn't that big of a deal. There are NO major theory breakthroughs. All 16 does is make certain technologies smaller (building plasma weapons the size of assault rifles, fusion plants the size of soda cans, etc..). It is TL17 that has the major stuff (i.e. Anti-matter, Portable disintegrators).
The Darrian Confederation, in the Spinward Marches, boasted of a TL16 navy. It really wasn't all that impressive. There was no real visible advantage over a TL15 navy (Sorry, no Jump-7!).
The only thing that TL16 siginificates is that the culture is now only 1 step away from Anti-matter.