The problem Orient already have is that their traditional fanbase doesn't live in the area anymore, because that part of london is cheap enough for immigrants to move into. It's the same for West Ham which is a big Asian/pakistani area now, West Hams traditional support has moved to essex.
As Orients fanbase gets old they will struggle to replace them as it is, the OS will just make it worse for them and possibly speed up the process. If you have to travel from essex to support a team anyway it's more likely that you'll chose the one in the big new stadium.
