This year, Oxford University Press will no longer be offering the Oxford Reference Online Core Collection; an official press release should be available in April.
At renewal time, current subscribers must upgrade to the Premium Collection or lose their access to Oxford Reference Online. In the meantime, current Core Collection subscribers can choose to upgrade to the Premium Collection until the end of their subscription period at no extra charge (when renewal time arrives though, subscribers will be charged for the Premium Collection). Pricing for the Premium Collection will be available in Spring.
OUP has been calling current Core Collection subscribers to get the word out; should you have any questions, please contact MINITEX.