The Japanese railway companies don't make prototypes for the lols. JR East's ALFA-X project will come to fruition with the E10, due to start testing in 2027 and enter commercial service in 2030.
Also of note in the announcement, is that JR East will run freight-only high speed trains, using retiring E3 Series trains (these are currently being replaced by new E8s). I remember that during the pandemic, the empty Shinkansens were used to transport fresh fish. As far as I can tell, this would be the first regular high-speed freight service since the French Post Office's TGVs which retired in 2015.