IMHO, if someone really thinks that a $100 lens isn't cheap enough, then perhaps he should buy a cheap P&S camera instead of DSLR
. 50/1.8III doesn't make sense to me, at all. I hope the new one will have USM in it.
Hmm, EF-S 28/30/35mm f/1.8 non-USM, very unlikely. I think that non-USM primes are history. How many of those were released in the last 10 years? Zero?
Zero in the last 10 years. The number of non-L EF primes in the last 10 years with USM? Also zero. It's quite possible that non-L EF primes are history, with or without USM. Consider - since the introduction of the EF-S mount, Canon has released just two non-L EF lenses, the two 70-300mm zooms (a focal range where the EF-S format offers no real benefit), no primes. Everything else has been EF-S or L. When they were designed, the non-L EF lenses were for consumers - they also shot FF (film) and affordable lenses were necessary. That need is now fulfilled by EF-S lenses.
As for the 50/1.8 II, I'm not suggesting that Canon would decrease production costs with a MkIII and then pass the savings on to customers. Like the 18-55 IS II and 55-250 II, the prices for the new lenses would stay the same or increase slightly (they can tout 'improved AF algorithms' which are basically free from Canon's perspective). The only point of reducing production costs would be increased profit per unit.
Actually, most of them were released in the last 10 years (all except EF 100mm f/2 USM in 1991)

EF 50mm f/1.4 USM - 1993 (not a ring type, but still

)
EF 20mm f/2.8 USM - 1992
EF 28mm f/1.8 USM - 1995
EF 85mm f/1.8 USM - 1992
EF 100mm f/2.8 USM Macro - 2000
However, I agree with you, there may be no future for non-L EF primes. Only L and EF-S will remain, but there is no future for non-USM EF-S primes as well. Canon yet have to make some cheap (affordable) EF-S primes, the market is starving for those. Current EF 28mm f/1.8 USM isn't any good for the price, Sigma 30/1.4 or Nikon 35/1.8 are much more attractive. IMHO Canon should discontinue all 5 non-L EF wide primes (EF 20mm f/2.8 USM, EF 24mm f/2.8, EF 28mm f/2.8, EF 35mm f/2, EF 28mm f/1.8 USM) and release some new EF-S USM primes instead. Like EF-S 20mm f/1.8 USM, EF-S 30mm f/1.8 USM and maybe an UWA - EF-S 8mm f/(something) USM.