Let's not forget the other unforgivable reason they may well put this lens out. Profit. Canon is a profit center first and foremost. That is there duty and they will sell thousands and thousands of these lenses with the IS feature included, making??? Profit... Good plan...
Profit is what keeps Canon in business, it allows them to invest in new technology and it secures a future for 'our' camera system.
5D3, 5D2, Sony α6000, G16 | EF: SY14/2.8, V20/3.5, 28/2.8 IS, Ʃ35/1.4, 50/1.8, 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, 70-300L IS, T28-300 Di VC PZD, Ʃ150-600 DG OS HSM S | E: SY12/2, 35/1.8 OSS, 16-70 ZA OSS, 55-210 OSS, SY300/6.3 ED UMC CS