“Which market segment is the one that is totally saturated with digital signage five years from now? (Is there a market where the gold rush is over and every new opportunity has been already taken?)”
Most, if not all, professional sporting venues will likely have digital signage throughout their space in the very near future – from concessions to in-game advertising, scores, replays, etc. Regarding our restaurant industry, there will be lots of smaller mom and pop locations that will never need or go to digital signage. However, most of the larger groups will have digital signage incorporated in their systems. There should not ever be a market that has exhausted every new opportunity for digital signage as long as digital sign technology continues to grow and improve.