If it’s ‘space’ in a cabinet, then presumably it’s FTTC , obviously as a commercial business, demand is predicted and sufficient capacity for that prediction is provided, you don’t over provide expensive equipment that may sit unused forever, this is a BT Consumer forum, they have no more say over Openreach’s provision of FTTC than any other service provider, if this extra demand is such that OR think it’s worthwhile, plans may already be in place to add new capacity .
If the cab in question is showing waiting list your choices are , keep checking, an existing FTTC customer ( of any provider not just BT ) may cease their service , thus creating a spare port , but you may not be the only person waiting , or hope that OR do have plans for expansion ( could just be providing more cards , or could be a completely new cabinet )
As far as 2020, the government has issued the universal obligations BT has to meet as far as broadband and that’s 10Mb download, something you will achieve anyway.
There are other network providers , if you cannot get what you want from a provider using OpenReach, try one of those , if they don’t serve your area, ask why not.
