If you don't care for the bag anymore then yes, sell it and buy something that you'll like more, but my answer would have been the same uneffected by whether the bag would be discontinued or not. If you still love it I would recommend you to keep it regardless of that fact.
Are you using the bag? Do you still like it? If the answer is no to both of those questions then sell but if yes then keep and continue to enjoy the bag.
Yes, I typically would sell as soon as something gets discontinued if not before Bc from that point it’s only a matter of time before it looks extremely dated and the amount you can sell it for will decrease from that time forward