If it actually gets to 80m within 5 years I'd consider it a success because they increased their current install base. Now if they struggle to reach 50m, that would be a tragedy.
50 million would be low.
In my opinion 50m+ would definitely be a success, failure is a strong term, to me it'd have to sell less then 25-30m to be classed as such, not 80m.
25 million is lower.
...to avoid getting banned for inactivity, I may have to resort to comments that are of a lower overall quality and or beneath my moral standards.