Having seen the show a few times with the postcards in, and a few runthroughs without them -- they do not use them in rehearsal -- they add absolutely NOTHING to the show. Their staging on the field is more or less out of the way, despite the fact that the printing on them is too small to read from the stands.
They ARE a distraction... in fact, for the morning show in Indy, Colts staff/volunteers actually pushed the postcards out into the end-zone DURING the Mandarins opener. I was standing in the tunnel leading into the stands (right around side 2's 40), and as soon as they wheeled them out, the entire audience turned their heads away from the Mandarins on the field to witness 3 colorful billboards-on-wheels being maneuvered along the endzone wall.
It's not too late to scrap them, but the fact is the orginaztion paid a fair amount of money to have them designed and manufactured. I highly doubt they would just throw away all that money like that.