This example assumes a conversation like:
A: What are you going to learn at uni?
大学で何勉強するの？
B: I'm going to learn French
フランス語を学ぶんです。

The Japanese translation is slightly awkward for the tense of a verb alone does not define the tense of a sentence definitively in Japanese.

In Japanese, tenses(the time of the action or state being described in a sentence ) tends to be expressed, not only by the inflection of verbs or ending particles but also, by words or clauses or earlier sentences that specifies time or place.
e.g
お祭りの日は皆で出かけて、花火見て、暑暑いと言いながら虫に刺されて、帰ってました。　（そして）家に帰ったら、スイカ食べて、叉花火をするんです。
On festival day, all of us would go out, watched fire work, and came back saying "hot, hot" while getting bitten by mosquitoes. (And) once we were back, we ate water melon and torched those small pieces of handheld firework.

The translation on the firework part is a bit of mess but that's not the important part. The part I would like you to take notice is the jumbled tenses in the Japanese sentences: the first sentence is in past tense, but the second is not.

In Japanese, once topic, subject, object, time, place are introduced, they sometimes persist and maybe omitted from that point on.

And the real hell and annoying part is this: PEOPLE OFTEN ASSUME TO HAVE INTRODUCED SUBJECTS OR OBJECTS OR TENSE EARLIER WHILE THEY HAVE NOT DONE THAT!!　
I used caps to convey you the exaggeration, excuse me if it annoyed you.

Anyway, when such happen, we have to listen to people ranting on about a thing that may be happening right now or happened or he thinks going to happen at one place or another to some unknown third person or... (My mother does this all the time sadly).

Surely, this sort of thing can happen in any language, but Japanese language seems a little worse than others at times.

Hence, "フランス語を学ぶんです。" by itself is a little awkward as a single sentence because the listener cannot be sure that the speaker have not left out any sentence that should be place before this; depending on contexts, the translation is fine though.

These are less awkward as a single sentence.
"フランス語を学ぶ予定なんです"
"フランス語を学ぶつもりなんです"
(大学に入ったら)"フランス語を学ぶんです"

Hi, CK.
I have translated them.
They are more definable and easier to translate because of key words like "the thing which I'm going to do" or "plan".

But, your question is hard and very interesting one.
1)I'm going to learn French.
2)What I'm going to do is study French.
3)The thing I'm planning to do is study French.

All different, of course, but...
Semantically they are roughly synonymous; I claim this because once you heard any one of them and if you were to explain what you have heard to another person, then your explanation won't be much different regardless of which one you heard.

Some people would never agree though, they would say being roughly synonymous does not mean the same; A subtle difference may cause the listener to reach a wildly different conclusion on what actually the speaker means.

But then, Japanese and English are too different for such nicety.

Semantically they are similar.
Grammatically they are dissimilar but once translated...
phraseology wise they are dissimilar: concepts are packed differently.

Personally I prefer linking as it would give users an option to compare and consider the difference, hell with rights and wrongs.
Practicality wise, with the current Tatoeba interface, a sentence having hundreds of linkage might proves to be a problem.