It's possible (probable, even) that the government would want to use a CDN for static assets (like fonts) for the same reasons that sufficiently-large private orgs would want to use a CDN for static assets.

In that case, it's also possible (probable, even) that some particularly-lazily-developed smaller sites would simply point to those same CDNs instead of hosting things themselves (much like how quite a few sites point toward CDN-hosted versions of jQuery and FontAwesome and such).

The only remaining step would then be for that taxpayer-funded CDN to cache any and all taxpayer-funded static assets.

Why not? It all depends on how important as an infrastructure CDNs will become. I know that in the States you prefer things to be privately held, but it's not too absurd imagining a future where CDNs are an essential and fundamental service to every day life for the vast majority of the population.