Ancient Teutonic, a highly inflected language, probably had a future tense for its verbs. But the Angles, the Saxons, and the Jutes seem to have lost it by the time they invaded the British Isles in the fifth and sixth centuries. The closest they came to speaking of the future was such statements as "I go tomorrow".
Word Ways: Vol. 15
, Article 16.
Available at: https://digitalcommons.butler.edu/wordways/vol15/iss4/16