When will SharePoint Classic Mode and Publishing be discontinued?

Hello all, 

We have quite a few on-premises sites in SharePoint classic mode with Publishing turned on. Currently we can migrate them to SharePoint Online also using classic/publishing, but I would like to know if we should start re-writing them in Modern without the publishing feature turned on, or leave them as is?

How long will SharePoint Classic remain an option in SharePoint Online? Also are there any plans to discontinue the Publishing feature? 

Thanks in advance!