With technology there is no upper limit on productivity.

But it will never be enough to satisfy all human wants and needs.

  We will always be able to produce more than enough.

More than enough for what purpose?

  We could do it indoors in skyscrapers with robots. You
  could grow enough weed for the whole world to chain
  smoke, in one building in the desert if it came to the
  point where that made sense (which it might in the
  nearish future).

Surely you understand that if we're using those robots and that skyscraper to grow weed, we can't also use those robots and that skyscraper to produce some other good. Surely you understand that less of some other goods would be produced because we chose to use that particular productive capacity to grow weed rather than to produce those other goods. Surely you understand that the raw materials, including human labor, used to build the robots and the skyscraper were not available to be used to produce other goods, and that the energy needed to grow the weed could not be used for other purposes. Surely you don't believe that human desires have already been fully sated, except for more pot, and that resources are just sitting around idle until jobless stoners get UBI money to buy pot.

  Capital is essentially imaginary and therefore limitless
  given the right incentives.

This is the first I'm hearing that capital is "essentially imaginary". What do you mean by that? What do you mean by 'capital'?