Chhhhhuuuuutttt! That would be a nightmare indeed. We'd have to go and dig mines like Minecraft and Space Engineers to find new sources... making me want to build another giant asteroid eater-grinder and a mega space station...
How to solve this un-sustainability development issue by instauring impermanence in the ressource? And where to go or what to do when there is NO MORE? Another planet (or map) maybe... Looks like we'd have to ride that Space Elevator after all ;)
Yes, harvest in space and use the elevator in reverse to acheminate ressources to our factories ?-) Also consider the mega-factories that we're making will be soon able to produce tons of increasingly sophisticated parts to milestone mega-projects... but what will them projects be?