It is retroactive, games that are already made today and already exist today on the various app-stores will be impacted.

10 ad impressions per user might not sound like much, but you're going to get a lot of people installing your app, not liking it, and uninstalling it. The way the mobile game business works the "install count" means almost nothing, you need many, many, many installs to start making any money at all because so few people 'stick around' to actually make you any money.

Regardless of how they spin it, this model is very bad for the FtP games, which is the vast majority of games now.