This is a textbook example of FUD.

Since NSA core mission is being ahead of everyone else, a claim that capabilities have increased a lot in the last few years is not FUD.

Without any specific evidence, it's still FUD.

What would specific evidence for "we don't know how much progress they have made since the last time we had concrete data about them" look like?

The FUD is implying they've made significant progress. You're right, "we don't know" isn't really a falsifiable statement, in this context.

Is there a certain time period after which we can say it's not FUD? Like if we go 10 years without any additional clarification after the Snowden slides, is it still automatically FUD?

I'm confused -- are you asking when an unsubstantiated claim is not FUD?

Not all educated guesses and reasoned estimations are FUD

None are, actually.

No claim of present NSA ability was stated. Noting the age of the data in question is a fact. Stating that an absence of new data creates a state of unknowing is a fact.

Fear of an oppressive government hacking the connection and arrest you. Uncertainty of agencies' capabilities given that they operate under top-secret levels with unlimited budgets. Doubt that they would stop working on or advancing the state of the art at defeating the security.

It seems a little unreasonable how much you are being downvoted, the parent comment uses uncertainty to cast doubt on the idea that TOR is safe from the NSA. That can easily invoke fear.

Unfortunately that is largely what we have to go off with the NSA.

And you just provided a textbook example of how the term FUD is usually applied.