Despacio was at Glastonbury in 2014 so if they could organise it then, no reason why they can’t now.
What would stop them doing it however is if either James Murphy or 2manydjs had other tour dates over Glastonbury weekend, as no way Despacio would happen for just one day given it requires setup, its own tent etc.
Just had a look at both of their tour dates and they are both free the whole Glasto weekend currently and as another poster has said 2manydjs are local around the time of Glastonbury, so could be a chance they do it. Whether or not it materialises is another matter