Black Mesa has been on the verge of release for the last 8 years of the 8 years of development, every time it has been pushed back or the release canned. Even if it does end up getting released this time, it isn't even the entire game in the mod.
Teams much smaller than 40 people have released games much bigger than Black Mesa in much less time. The entire project is flawed by either a lack of ability, lack of motivation, lack of organisation or a combination. It is more likely we will see HL3 before Black Mesa is fully released