Any change in the golden visa will be part of the national budget law. When the 2021 budget has passed parliment, it will be published on www.dre.pt, the Diário da República Electrónico.
The site gives choice of Portuguese or English. Use Portuguese because when searching using English there are far fewer results. That’s because the site returns only pages that were submitted to it in English. To find the 2021 budget search this: “Orçamento do Estado para 2021”. To locate golden visa info, search the untranslated page for “Autorização de Residência para Investimento”
 Chrome browser translates using Brazilian Portuguese. To use European Portuguese, go to Bing Microsoft Translator. Paste the URL into the left hand box. Clicking on the URL in the right hand box opens the translated site in a new tab.
Example of search results for the 2020 budget: Legislação Consolidada - DRE