Don’t get too excited to see our fluffy ram friend at Worlds this year, as he won’t be making any appearances. In a post by gameplay designer Andrei “Meddler” van Roon, he noted that Ornn is releasing too soon to have him at Worlds.
Been seeing the question crop up occasionally of whether Ornn will be playable at Worlds or not. It's an issue we went back and forth on a lot ourselves, our conclusion at the end though was that he shouldn't be available. His release is only a couple of patches before the Worlds patch (7.18) and he's got a lot of distinctive stuff on his kit that could take a bit longer than usual to assess the impact of, upgraded items for his allies especially. We're really excited to see him in pro play, want to make sure we've had time to do any polish that's needed though.
Like most new champ releases, Riot will need time to polish his kit and make sure it’s the best it can be for competitive. These changes typically take place over weeks and many patches, so he probably won’t be in good shape for Worlds.
The next time we will probably get a chance to see him in competitive play is during the All-Stars event at the end of the year.