I doubt it will ever be. First of all, Spark development is currently dead. And personally i think there are more pressing issues and interesting features than doing a centralized emoticons management. Also, it would include infrastructure work (hosting emoticons) or changes to Openfire (if you want to manage them in the Admin Console). There are only a few volunteers keeping an eye on the services here (well, and one from the Jive).
All we can do is to include your created pack in the next Spark build, so it would be a bit easier to distribute, with the new Spark version installation.