So far, Delta hasn’t extended seat blocking out past April. It sounds like you are traveling with a companion? If they had extended seat blocking, I’d say roll the dice and be happy settle for a whole row to yourselves in C+ since service in F isn’t all that these days, but they haven’t indicated that they are extending blocking any further.
The June schedule has not yet been finalized, so your flights have a good chance of changing (including consolidation of flights, which might lead to the flight being more full).
My anecdotal experience has been that travel has been picking up, and with a third of adults having received their first dose of the vaccine, travel may be up further in June.
$90 worth of SkyPesos isn’t a bad price for that route, but since we don’t know what Delta First will look like in June, I wouldn’t pay for upgrades right now. OTOH, with devaluation, maybe it’s time to cash out!