And no one will be able to run it for 2 years.

Though looking at developer.android.com it does seem that it would be safe to target 2.3 as a minimum.

http://developer.android.com/about/dashboards/index.html

Unlike with iOS where it is easier for users to upgrade their OS if their phone supports it, Android version upgrades come most often when people upgrade their phone and that means at the end of a 2 year contract for most people.

Targeting the most recent Android version seems like a poor way to get people to use your app.