Two reasons it won't end the world. 1. This is in vitro work, and even there it is only 5x as efficient. In vivo I'd expect that rate to go down. 2. Metabolis

Two reasons it won't end the world. 1. This is in vitro work, and even there it is only 5x as efficient. In vivo I'd expect that rate to go down. 2. Metabolism is expensive. This is probably not a very fit pathway. It takes a lot of energy to produce the proteins and ATP necessary to power this cycle and it's product isn't more ATP. It would incur a substantial fitness cost and in the wild it would likely get out grown by wild bacteria that favor Glucose producing photosynthesis. Not that a new ice age couldn't happen, but carbon fixation is already at a evolutionary local maximum among the six different wild versions, so I don't see why a 7th would be any different.