What does the phrase "before too long" mean?

It means before it takes too long time. In your example it may mean in 1-2 years.

In addition to what Jay said, sentences like this are usually a kind of emphasis. “before too long” figuratively means the exact opposite of “a long time in the future”. This double negative (which is a form of understatement) is called litotes.

It’s the same as saying “not bad” when you actually mean “quite good indeed”.

Interestingly, the same exists in most other languages, and has probably always exists. For example, in Latin there’s the idiom “non ignoro”. “ignoro” means “I don’t know”, and “non” is just the negation. Thus, “non ignoro”, though literally translated as “I don’t not know”, in reality means “I know exactly“ (with emphasis).

While others have explained the literal meaning of "before to long" being "soon", I would like to opine on when it is used. The phrase "before too long" is one of hope that something will grow under it's own momentum. Word to spread, crops to grow, etc. Phrases like, "Well, we've planted the corn, before too long we'll be taking it to market." Or, Boy, you keep eating all that corn, before too long you'll be bigger than me!"
This is opposed to the phrase, "It won't be long now" which is used in pessimistic ways. "Grandpa's been sick a long while. It won't be long now before he eats is last piece of corn."
But they are English phrases, so of course they are also used the reverse of what I just said. We like to keep you guessing.