Yes, the dealer will update for free under warranty. I scheduled mine yesterday for Friday appointment and I am in the 3yr/36k warranty period. They confirmed it would be free under warranty.
Out of warranty my dealer says they would charge the cost of one hour of service which is likely over $100.
Do a search for old TSB 15-205-16 in the forum/thread and I believe you will find a link to an old TSB with instructions on updating the firmware. However, the instructions will no longer help us since we don't have access to download the latest firmware from Subaru and this has not been available to share on this forum from other members. Hopefully somebody will be able to share down the road. Keep in mind each type of radio has a different firmware, so making sure you have the right one for your model year & radio style is very important!