Dpreview interviewed a bunch of Canon managers and here are some info:
There are actually no technical reason why the EOS-M50 couldn’t have Dual Pixel AF in 4k mode:
“With the EOS 5D Mark IV, we do offer 4K video and Dual Pixel CMOS autofocus, so technically it is feasible. But given the position of the M50 in the lineup, we can’t include all of the features available in a product like the 5D IV. Given the position of the product, we wanted to achieve the optimal balance [of features] in a camera in that range. We’ve optimized the M50 as best we can [for its market position], and within those parameters, the combination of 4K video and Dual Pixel CMOS autofocus was not possible.”
About the future High End Mirorless:
“The new M50 is an entry-level model, because that’s where the high-volume sales are. We want to establish ourselves in this market, and then move forward [from there]. In accordance with the full lineup strategy, we will be tackling [the mid-range and high-end mirrorless market] going forward.”
…and..
“We still believe there’s work to be done before we can achieve the level of satisfaction that our users are looking for before they could confidently move from DSLR to mirrorless”