Hot on the heels of the Intent to Ship for Chrome, here is news of Firefox, they intend Grid to ship without needing a flag enabled in Firefox 52.
Note the discussion about subgrid here. I am very keen that we do get subgrid support for grid, the feature is marked as ‘at risk’ in the spec and no-one has yet implemented despite a revised version of subgrid being discussion earlier this year. If you have use cases that would be solved by subgrid, I’d be interested to see them in order that we can get a better idea of how this would be used in practice.