This is sad, but it was definitely the right call.
And it is a postponement towards the end of November, not an outright cancellation. For those who have never heard of Pixels Camp, it is the largest and most popular Portuguese hackathon, and one of the few technology events that would lose a lot of impact by moving to an online-only model.
As I type this we have
31 39 confirmed cases of COVID-19 in Portugal (all detected within one week), with 300 339 others in various stages of assessment, vigilance or preventive quarantine.
Most notably, the President of the Republic has self-quarantined.
Many of the above are in the northern part of the country (including at least one college campus from which hail many of the hundreds of students that travel to the event every year), and largely linked to trips to Italy (business travel there is common in that part of the country, which caters to fashion and shoe industries).
Both government and the medical establishment have been stepping up public awareness and preventive/reactive measures (field hospitals are already in place, some schools have been closed, etc.), but everything points to figures climbing steeply over the next few days and weeks, and there will certainly be criticism about delays in taking action.
Fortunately, we have a national health system that (mostly) works, doctors at key hospitals/medical faculties are openly sharing internal planning and awareness sessions on YouTube and there is an open debate about remote working and how the government will support people who have to be quarantined–which is a vastly different situation from, say, the United States.
Wash your hands, people. That is the best thing you can possibly do.