When has it been revealed that it will be a limit of 12000? your making an assumption based on f*** all at the moment as there is nothing to base this guess on. So far all we know is that there will be a new stadium in Failsworth that will initially hold 12000 and it will be designed so it can be expanded, to what extent it can be expanded to I don't know you dont know and at this point maybe the owners, designers and builders may not even know yet.
But if you would like to express your dissapointment about this without knowing anything but assumptions rather than FACT, you keep on doing so.