I wonder what the limits of a "pancake"'lens are. Could they make a 14mm or 85mm pancake?
Since Pentax can make a 70mm f2.4 Pancake and a really small 15mm f4.0 for APS-C, I think it is not completely impossible but the Limiteds are a bit pricy unlike the EF40.
Wait till they include diffractive optics into the mix
5D3, 5D2, Sony α6000, G16 | EF: SY14/2.8, V20/3.5, 28/2.8 IS, Ʃ35/1.4, 50/1.8, 50/1.8 STM, Ʃ50/1.4 EX, 100/2.8L IS Macro, 16-35/4L IS, 24-105/4L IS, 70-200/2.8L IS II, 1.4x II, 2.0x III, T28-300 VC PZD, 70-300L IS, Ʃ150-600 OS HSM S | E: SY12/2, 35/1.8 OSS, 16-70 ZA OSS, 55-210 OSS, SY300/6.3 ED UMC