Hi Ollie -
We love CSS Grid and think it enhances Foundation. Being able to use it with a class based system be valuable to most especially when prototyping rapidly. Foundation has a history of integrating and helping push forward new technologies and CSS Grid will be another on of those: zurb.com/blog/happy-birthday-foundation-five-year…
We have a lot of plans and ongoing discussions regarding the JS architecture for the future of Foundation. Web Component will be a supported approach, like with Polymer. For more on the JS architecture, @kball posted a great description of it here: hashnode.com/ama/with-zurb-foundation-cj4ad29vl00…