u/Ill_Investigator_886

The engines on the Flight 3 booster look visually different from the earlier BE-4s, and Blue employees have hinted that Block 2 development is basically done (from LinkedIn, we know work on it started no later than July 2023, so that’s close to 3 years of development already). Finally, the 9X4 webpage also explicitly says it'll use Block 2 BE-4s.

Credit: Max Evans

Looks like Blue is investing heavily in the reusable upper stage. Hopefully, we’ll see a demo flight within this decade.

Source: https://www.linkedin.com/in/petemichalakos/recent-activity/all/