and that is the problem with collecting Roman / ancient coins! Never know when a hoard will kill the value of ones collection.
If I remember correctly the value of a number of Morgan Silver dollars dropped when a hoard was discovered some years ago. It happens.
I doubt their price will drop. late Third Century Antoninianii are already extremely common, in large part due to the hyper-inflationary condition of the Roman economy at that time. There are literally millions of these types of coins, and most of them are probably still in the ground waiting to be found. Coins of Carausius and Allectus will be quite valuable though, as they are pretty scarce and they have a British connection (they were were seccessionist rebel British Emperors) so they are quite popular with British collectors especially....