Individual teachers might mine company web sites for their lesson plans, sure. Another likely design pattern is companies offering modules at different grade levels, perhaps a free version surrounded with purchasable services leading to a credential of some kind.
Textbook publishers provide a relevant model or prototype, although here we're replacing traditional wood pulp with bytes and pixels, meaning even small engineering firms might get into the game.
We might also have a Subway concession in the school's food court, and/or maybe a Noah's Bagels.
Note that shopping for curriculum segments and putting them together in creative ways could still be under local control, the responsibility of academy faculty.
I would encourage not abdicating this responsibility, plus devising democratic ways of collaborating with both students and their families, with the details left to the players (various templates available).
Even an extremely remote school depending on the Web for most of its content might nevertheless earn a reputation for creativity and curriculum writing effectiveness, based on what the school's in-house web wranglers had wrought.
What accredited schools provide that homes need not is a controlled testing environment. The private sector is already used to credentialing over the Web, but typically depends on administering tests in a safe and secure environment where (a) no bullies take unfair advantage and (b) well-meaning guardians don't get to back seat drive.
Congrats to Dave Koski on his new 4D Golden Spiral (made of T-modules).
image by DK in vZome
