A switch to Discover for debit was inevitable - Cap1 is no longer subject to Durbin debit caps (issuer-is-network exempt, Cap1 now owns Discover). You could try calling and seeing if they will undo it or issue a new Mastercard. I'm not sure if any exception policy exists, but there might be a possibility if they think 90% of people will be fine with it but want to retain the 10% for which international debit usage is important. (%s made up, I don't work for Cap1, but if they thought a non-insignificant portion of people were using debit abroad that would leave over it they'd probably have offered it as a voluntary switch with a carrot like 1% cashback.)

For credit it becomes a far hazier conversation. Conversion of the non-travel focused cards becomes far more likely, but there isn't as massive of an interchange advantage on switching credit to Discover. Sure they don't have to pay network assessments but it's not as nearly as stark as going from 0.05% on debit to 2-4% debit cap exempt. My opinion is that Cap1 is likely to issue some personal cards as Discover to extract concessions from Visa/MC to not convert the entire portfolio. Cap1 already has a ton of credit issuance from Discover itself so it's not like they don't have a very active base for NOVUS (Discover's credit network) already... If Visa/MC don't give the concessions Cap1 wants not difficult for them to replatform the non-travel cards.

Cap1 talks good game about expanding international issuance but I remain skeptical of their ability to do so. Time will tell.