Based on artificer, mount, and certain power (e.g. Flaming Sphere) rules, I predict one or more of the following will be implemented:
1) shared actions, i.e. you OR the companion/pet can attack, move, etc.; applicable if it's quite powerful but there will be no loss of XP earned.
2) independent actions, i.e. you and it get complete suite of actions; this is balanced if, as per intelligent/powerful mount rules, it gets a share of your XP; this will probably be rare because aside from balance 4e tries to minimize certain players hogging too much time during their rounds.
3) minor action to direct; applicable if it has modest and/or limited use effects.