When talking about something that is next in a time sequence, such as when meaning "upcoming," the most common word used is próximo.

When to use proximo vs siguiente?

Although both words refer to a relatively close future, they are a bit different in meaning because they take separate time reference points: próximo refers to the future from actions that start at the very moment of speaking. ... siguiente takes a previously-mentioned time element as reference point.

How to use proximo?

Proximo Systems is leading the way towards a new and more personalized approach to communications for enterprises and carriers. The Moncktons leave us this evening, and Amelie intends to set out for the hills on the 6th proximo.