HRVs don't really cost that much to run. Probably less than than having a real leaky house. I'd rather have a filtered source of fresh air and a means to exhaust stale air than rely on poor building details to let air leak in and out of my house uncontrolled.
Power outages? Like already said, open in window. If the power outage is more than a week, you have much bigger issues than fresh air. I have a backup generator setup and a 1k gallon propane tank so I'm not super worried about it.
While energy savings are a big part of it, they aren't everything. You have to live there too, not just pay the bills. Comfort and health is a big part of it and a tight, mechanically vented house will blow the doors off a leaky house in that aspect.
That's everyone's kneejerk thought, and where the codes are inevitably headed. However, I have a problem with the idea of a dwelling that requires a 24/7 artificial means of ventilation. Where's the energy savings in that? How are you and your house going to stay healthy through an extended power outage?