I hope Firefox implements a great and robust tab grouping feature. Because they used to have one that worked beautifully.
Firefox used to have Panorama view, which was a way to group tabs with a nice visual interface. ...and they removed it because not enough people were using it.
...Well if you stopped removing useful and perfectly functional features, maybe you wouldn't need to rebuild them later when it turns out people do want that feature, huh, Mozilla?
There's an extension that reimplements Panorama and it kinda sorta works like it used to.