Jess agree it sounds ridiculous and maybe a threat to business as usual, but this will happen at some point whether we like it or not. Demand creates offers and trying to stop it will drive the people with the demands to somewhere ells where they can get the offers.
I'm not in favor of prohibiting, we can't stop evolution from happening, we just need to adapt.
Everything is getting automated to a certain degree, even art production itself, we can see this already happing in film, broadcast, visualization and game productions.
Look for example at this game (http://www.no-mans-sky.com/).
Here we can see an example of a software that's capable of generating entire worlds, just out of a library of relatively few things. Rest assure this kind of software and its output will definitely get way more advanced.
Inexpensive software that will generate most common known plants in a matter of seconds by just entering its common name or click a picture (in form of a plug-in for most major 3D packages) will certainly arrive at some point.
This doesn't mean there will be no future for stock media (on the contrary), but things will certainly change for some types of media that can be generated quickly/easily and have no additional added value to offer.
I think a market for both types of media will go hand in hand because all this automation will enable smaller teams to take on bigger scope of projects, resulting in more projects taken on.
Everyone has different preferences for doing things, there is always room for creativity and improvement, evolution keeps us driving forward, it keep us innovating so that we don't stay stuck in the same place and keep doing things the same way.
I'm glad it is so ;-)