No; UK domain owners will be prevented from renewing their domains, but it doesn't say they'll automatically lose them. From what I can tell, if you renew just before March 2019, you can keep your domain until 2029. Although, the Registry will be able to revoke them, so it's not guaranteed.
Comments
The rules say: EU, or Iceland, or Norway, or Liechtenstein.
The rules say European Economic Area (https://en.wikipedia.org/wiki/European_Economic_Area). Which the UK is, ridiculously, also leaving, but does include Iceland, Norway and Liechtenstein as EFTA members.
FWIW, the Domain Name Registration Policy (https://eurid.eu/media/filer_public/76/48/7648e621-0c5d-4c09... , linked from https://eurid.eu/en/register-a-eu-domain/rules-for-eu-domain...) doesn't mention EEA; it spells out the 3 extra countries explicitly.
also, the rules are not set in stone
Until the rules are changed, UK domain owners will be thrown out in March 2019.
No; UK domain owners will be prevented from renewing their domains, but it doesn't say they'll automatically lose them. From what I can tell, if you renew just before March 2019, you can keep your domain until 2029. Although, the Registry will be able to revoke them, so it's not guaranteed.