My experience in the DC area with Panera is that the cashiers don't speak English very well. Using the kiosks will allow them to hire more non-English speakers to staff their restaurants at lower wages. No doubt there will also be personnel reductions.
I don’t know if the portions are getting smaller or not because I only ate there a couple of times.
But I can tell you if the Kiosks work out replacing cashiers the first time the minimum wage goes up there will be layoffs.