One of the structures denoting the future in Sanskrit is the so-called -tā́-future, based on an agent noun and a present tense copula. Typologically, this grammaticalization path is unique. In this paper, this astonishing fact is tied to another unique feature of hysterotone -tŕ̥-nouns, their situative semantics, which forces a presupposition relating the event depicted by the noun to another event taken from the context. In ambiguous contexts, this relation could be (re-)interpreted by hearers as one between the event and the speech act itself. The grammaticalization, then, is hearer-based and triggered by semantic reanalysis. The process is essentially identical to phonemicization. The scenario developed in this paper thus further strengthens the position that grammaticalization is ontologically not distinct from other types of language change based on speaker–hearer interaction.