They could copy IOTA which is supposedly already quantum resistant.  The problem with Bitcoin is not really identifying the problem or the solution.  It's that as it grows bigger and bigger it becomes harder to upgrade without disrupting the existing network.  It's like having a fully loaded 18 wheeler traveling down the highway and trying to transform it into a 747 jet little by little without stopping. MAYBE it's possible but it's a lot easier just to build a new jet.  I think to get Bitcoin to the point of being agile enough to adapt for these and other yet unknown threats there will have to be a lot of hard forks until we get to a point of a totally different Bitcoin than we currently have. Most of the problems with bitcoin could be fixed with decentralized governance with decision making power and budgets for development but I don't know if Bitcoin can get there before forking itself out of existence.  Also I think some form of nomenclature should be adopted for the minority side of new bitcoin hard forks so that we don't have 30 or 40 different bitcoins around like BitcoinNew, BitcoinCool NewestBTC etc. because this confuses the market. If we named each fork something more standardized like BitcoinHF25_10_2017 people would still see it as being an official part of Bitcoin as a whole and when people used one of the forked bitcoin networks it would seem closer to using a different version of a software rather than seeming like using a knock off version, the way it would seem if we have BTCPlatinum, SuperBitcoin and whatever other names people could think of for a fork.