Both the Cambridge Grammar of the English Language (CGEL) by Pullum and Oxford Modern English Grammar (OMEG) by Aarts clearly say that the progressive futurate (i.e., the present progressive indicating a future event as in *I'm leaving next week*) does not have an aspectual meaning to it.

OMEG on page 270 says:

> 
> It is important to be aware of the fact that [the progressive futurate] is not aspectual, that is, the situation is not regarded as unfolding over time.
> 
> 
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What exactly does this mean?