UK just left the EU this year. With Brexit being fully done by the end of 2020 I don't see any chances of the GBP to disappear. The UK is looking for independence, which includes a fully sovereign country with it's own currency. In my opinion we will have GBP around for a long time. Which doesn't mean it's going to be an important currency. The aftermath of Brexit will only be visible in the years ahead, the economic drop back should be quite large which will bring down the Pound even further. It's very likely to see the Pound below 1 EUR in the near future. Which is probably also what the UK wants, as it's trying to get it's export back up. A weaker currency will make UK products cheaper for Europeans and the rest of the world.