I don't think energy consumption will be the downfall of bitcoin, but it surely will affect bitcoin if from time to time there will be mining sites that need to close down due to high electricity consumption.
Bitcoin really consumes a lot of electricity in mining which was the usual issue during the past months already. There was even a news that a mining site related to bitcoin was forced to close down because China's government has been reserving their power consumption. Maybe this scenario will make the mining corporations to slowly switch from being eco-friendly. Correct me if I'm wrong, but I think bitcoin consumes still lesser energy compared to big private mining corporations and companies. IMO it shouldn't be a big issue. Although I really do hope that mining becomes more environmental friendly since I'm also aware of the repercussions it may cause to the overall state of our planet.