The rumors need to start materialising as lenses. The newer cameras (before we even get to 45 or 85MP as been rumored here) such as the 6d show up the problems of the EF-17-40mm f4L, EF24-105mm f4L both of which have pronouced chromatic abberations at 17mm and 24mm respectively. As sensors improve the faults of lenses masked at 8, 10, 12 or 18MP now show up and this undermines the system ability to produce great results. Sigma have shown improvement are possible (so has Zeiss at a price) and still remain competitive to Canon pricing.
Canon 5DS, Canon 6D, 16-35 f4L IS USM, 17-40 f4L USM, 28 f2.8, 24-70mm f4L IS USM, 24-105 f4L IS USM, 100mm f2.8L IS USM, 70-200 f4L USM, 70-300 f4-5.6 IS USM, 50 f1.8 STM, 100-400mm f4.5-5.6L IS USM II, 1.4EX III, Canon G7 X, EOS 760D EF-S 10-18mm f4.5-5.6 IS STM, EF-S 18-55mm f3.5-5.6 STM