I would love a G-Unit group album for my own tastes. Banks and Yayo always thrived in a group environment, where they were being guided and only had to be counted on for dope verses. 50 is a natural leader, Buck brings a certain charisma, and Game can pick beats with the best of them.
However, I think people like me are in the minority, and even if this album came out, I don't think it would have 1/10th the impact the original Unit did. People have moved on, and it would be kind of sad to see these dudes reunite on some "we're gonna shut the game down!" shyt, only to find out that no one cares. Which is why I think the Dipset reunion hasn't happened, they sort of know that it's better to talk about it than it is to do it.
In other words, better to just leave it alone. Game may not be the star he used to be, but dude still moves some units and has a seemingly dedicated fanbase that will keep him eating for years and years so long as he continues to provide them with product.