It's also worth pointing out that 'stopping breeding' is a very different thing from 'stopping keeping'. I'm not sure how recently they had a calf, but SeaWorld could potentially still have Orcas for the next forty plus years.
So much could happen in that time. The decision calculus will change and future management will not feel bound by this decision for ever.
Additionally, although the announcement is not specific on this point, the following extract is noteworthy:
SeaWorld will increase its focus on rescue operations — so that the thousands of stranded marine mammals like dolphins and sea lions that cannot be released back to the wild will have a place to go.
Seaworld have rescued Orcas and not released them fairly recently. They may well continue to do so.
It will be interesting to see if activists now push for sea-pens or if it falls off the table as a perceived victory. Whether or not you agree with Orcas in captivity, virtually all of us will bemoan the loss of the Blue World project. It's a shame they won't go through with it anyway. An aquarium will surely always find a good use for a large tank.