Indeed, the first commercial SON lamps were installed over 40 years ago.
4th September 1967: A workman puts the finishing touches to new 'Gec-Osram High Pressure' street lamps in Southend, Essex. They are some of the first to be installed in the country. (Photo by Harry Todd/Fox Photos/Getty Images)CosmoPolis MH offers efficiencies and lifetimes comparable to SON. Given the use of white light allows less lumens (and hence watts) for the same perceived brightness as SON, and Cosmo always uses electronic gear which is more efficient than SON magnetic gear, there really isn't any justification for the use of SON in new PFI schemes considering the amount of lanterns being installed and their expected lifetime.
Investment in SON technology has ended, the future is in CFL, MH and ultimately LEDs, however the current LED technology is only a stopgap until OLEDs (Organic LEDs, flat panel and flexible) come along. The different construction of OLEDs finally overcomes the heat dissipation issue with "conventional" LEDs.