It would certainly bring a lot of attention to cryptocurrencies if any major economies adopted central bank digital currencies and these won't likely render it obsolete because it has a unique value proposition and limited supply and is decentralized in nature which makes it an individual store of value that continues to redefine itself as it evolves so there's not likely to be much competition from such endeavors even a Facebook cryptocurrency won't likely detract that much from its growing niche and instead lead to a potentially wider and more conscientious market recovery as more and more adoption occurs with a focus on only the best quality innovations on offer