There's no mention of the current test site at forecast-v3.weather.gov nor api.weather.gov, both of which still function.
I'm continuing to offer both the V4 (old script) and V5 (JSON script), and include the V5 script with the Base-USA template. The V4 script is only for sites who've consistently encountered issues with getting point forecasts via the V5 script/api.weather.gov.
No need to panic.. all remains as is for now while they plod along to implementation of the forecast-v3.weather.gov into production. ETA unknown. (but 2 years overdue)