The matter of pollution has been discussed many times, and there's enough info online (including fact-checking services) that show it's not a real ecological threat, and, on top of it, it's all a matter of sources of electricity, which need to become cleaner, rather than of consumption. Now, regarding the dead end, I don't understand the argument. You mean it's a problem because energy consumption is rising? It's still far from the levels that pose a problem of the lack of electricity, not to mention that miners can choose to opt out, difficulty would decrease and so would consumption. Not to mention that your calculations don't match those of franky1, so providing sources with estimates would be nice.