When is the hardfork planned? I think it would be a good time before BTC hardfork. As we could see ETH and alts grow if they would have made this in few month before BTC hardfork and than will be BTC growing... 
7 December 2019.You can read this: https://blog.ethereum.org/2019/11/20/ethereum-istanbul-upgrade-announcement/
or this: https://cointelegraph.com/news/istanbul-to-berlin-ethereum-milestones-on-the-road-to-serenity