1. A vehicle comprising: a powertrain including a battery-powered electric motor, an internal combustion engine, and a transmission; and a controller programmed to permit an upshift of a transmission gear ratio while a powertrain torque demand is less than a forecasted available powertrain torque sustainable over a predetermined upcoming duration of time, and inhibit an upshift of the gear ratio while the torque demand exceeds the forecasted available powertrain torque to reduce successive gear shifts.