I disagree. I don't own a Vita, but I'm fairly certain it will sell more than 20m in ten years time. It's only been out 7 months in America/West Market and has sold 3m. Let's say it sales 5m total in its first year, multiply that by ten and you're already at 50m, and that's just a rough estimate.
This doesn't include things like price cuts and the eventual Vita remodels that will boost sales somewhat. So it should be able to sale 20m by year five or six.
Zero Escape: Virtue's Last Reward = best game ever made.