John Compton has posted more details on the Concordance changeover:

The following apply to those switching to the Concordance faction:

• This change costs no Prestige Points.
• You keep any benefits earned on your previous faction’s Faction Journal Card, but after changing factions, you are no longer able to fulfill goals on the previous faction’s cards.
• You keep any faction-specific boons earned on Chronicle sheet as part of your previous faction.
• If you have a faction trait for your former faction, you have two choices: either keep the trait or replace it with any one of the Concordance faction traits.
• You lose access to any purchased faction-specific vanities.
• You should perform this change either by August 2nd, 2018 or at the beginning of the next adventure the character plays, whichever occurs last. If during this time you play a scenario that includes a Concordance faction-specific objective and reward, you may switch to this faction at the end of the scenario and potentially earn that reward. This allows a PC to experience what the Concordance values firsthand, make an informed choice, and switch to the faction without missing out on the reward.

Our original post on the new faction has been updated to incorporate this information.