Whilst it wouldn't be as popular as today, I don't think it'd massively cripple the success of the series, and anime in the west in general. The series was already massively popular in most European countries long before English speaking ones got it, which would kept the manga's sales comparatively close to what they are today.
Even though DB caused a boom in anime for English speaking countries, the influence was already there with Pokémon, of which was far more popular than DBZ during the 90s.
Worst case scenario would be that DB becomes a manga for the less mainstream reader, much like the other titles of it's time such as Hokuto no Ken and Saint Seiya. Given it's popularity in other countries, I still doubt this though, especially since if 4kids were to still dub OP or Naruto's dub still came about due to the popularity of other anime, it'd eventually lead people to Dragon Ball due to the influence it had on both.