But that's not true - "soon" does not absolutely require the future tense, it's just usually not very idiomatic. In context, it can work perfectly well in English. And if the Swedish sentence is idiomatic, I believe it should be taught even if the English gets a bit clunky.
That said, it's perfectly possible that I'm wrong, or that there are better options at teaching this. It'd also be great if Duolingo offered an explanations system to put by individual sentences.
FWIW, the English here actually is grammatically correct, it's just a case of a strange verb tense that is rarely used in English (I'm not even sure what it's called formally).
Essentially, this is a hybrid past/present tense in that's relating events that have happened as if they are currently happening. It's only ever used in prose and when retelling stories, and even there it's pretty rare, mostly being used for stories told from a second person perspective (the primary examples being the old choose your own adventure books that were really in vogue here in the US during the 70's and 80's, and the interactive fiction and JRPG games that evolved out of those).
It's called "present tense with future meaning" and English has it a lot. For example "My train gets in at five." is perfectly fine. Hardly anyone would say something like "My train will arrive at five." In writing, this might be different but in spoken language this "tense" is used a lot.
I do agree that the English translation in this specific case sounds a bit clunky but I think that's more to do with the soon being at the front. This, in turn, has been done so that we would put snart first in the Swedish. And as the Swedish sentence is what we all came here for, I agree with devalanteriel - due to the reciprocal way that duolingo works, it's sometimes necessary to sacrifice English style in order to teach good Swedish. Remember, languages usually cannot be transposed item for item from one to another.
We do accept that as well, though, in addition to a full range of other phrases. But like I noted to Kats, we need to put something that'll yield the idiomatic Swedish phrase as the default translation, even if that means the default English translation won't be idiomatic.
You're here to learn Swedish, though. If using unidiomatic English will teach the Swedish phrases better, then we are going to use unidiomatic English. We still accept other translations, just not as the default. As long as Duolingo doesn't change their system, we'll have to keep doing this.