[Grammar] It will not be long before you get well.

[wotcha]

"It will not be long before you get well"
I found this sentence from my grammar book and wonder why we don't say "It will not be long before you will get well"

 

[SirGod]

*Not a teacher

It is correct.

It will not be long before you get well.

The highlighted clause is temporal (before introduces a temporal clause). We never use future tenses in temporal clauses. In order to express the future in temporal clauses we use present tenses.