Jira Dashboard Item

I was going through a tutorial for jira gadgets but it said that soon, gadgets will be replaced by dashboard items. Approximately when is this change going to take place? Considering the very little documentation provided on items compared to gadgets, would it be better right now to work on a gadget or item?

Furthermore, I could not find a lot of documentation on dashboard items and just one tutorial that just merely touches the surface of the topic. Kindly share some documentation as well.