Photo by Alexander the Great (FLICKR / INSTAGRAM ). Click for a larger version.
The Sixth Street Viaduct Bridge, one of the most photographed and filmed in Los Angeles and thus the word, is likely to collapse in the next 50 years, and will be replaced. Construction is set to begin in 2015 and will take three years to complete. The new bridge looks to have the potential be even more iconic than the existing structure, and possibly includes "public art" and a viaduct park.
Fore more on the history of Los Angeles bridges, check out this excellent post from Nathan Masters for KCET.