[mjdwitt]

It does indicate a concept of future. What it doesn't do is use a different tense—the key verb is the same as when talking about the present. It's a subtle distinction, but he is arguing that this lack of differentiation in verbs has an impact on internalizing future events.

And while you very well could make the translation from whatever the original was to "It will rain tomorrow," it might not be a literal one that preserves the original tenses, which would obscure exactly what he was trying to point out.