I'm not sure how far the next surge will go, because I'm not convinced that Coinbase has the hardware infrastructure to handle the volume. They have been getting slammed, and during each feeding frenzy (most recently, Bitcoin Cash), the site crashed several times. Wire transfers have been delayed, and have taken as long as 10 days to settle. Hopefully they will be able to grow the network quickly enough to handle what is in store for 2018.