I see you can define releases based on estimations and team(s) based velocity. does the portfolio plugin use similar values/calculations for uncertainty like the 'Version Report' plugin?
That plugin uses average velocity and uses that to estimate a predicted, optimistic and pessimistic completion date.
Portfolio is currently looking at the velocity, estimations, priority and, potentially, skills and stages. There is currently no uncertainty mechanism baked in the Portfolio algorithm.
Portfolio does offer the ability to have multiple scenarios that you can use for best/worst case planning which could achieve your goals.
I'd be interested to hear more about your use case as we're interested in bringing smarts and insights in Portfolio to the next level while making it easier to use!
