Do you know that Firefox now has a new technology that simplify the development of an extension? And also use and extend the API of Chrome? Yea, I am serious you can do the same extension for many browsers!
WebExtension are the future for addons in Firefox but this is not enough because they works also on Chrome, Opera and soon Edge without any changes!
Think about it, the cross browser addon issues is only an old nightmare! In conclusion because all this amazing news and how it is easy to extend Firefox will be available new APIs to customize the Firefox experience in this year.