Yes, this is possible.
Once they are in their portal account, they can update their Card details by selecting the 'Edit' option from under the Payment Method Information (V1)/ Payment Methods(V2) section in the portal. Screenshots below.
Customer Portal V1
Customer Portal V2
If you're not using the Customer Portal, you can also email customers with a secure link asking them to update their payment details. This can be done using the Request Payment Method option on the customer details page.
Here's more on that.