when will elementary OS get kernel 4.10 as part of the default installation?
It is not at all likely that 0.4 loki gets kernel 4.10 as the default kernel. However, you can install it via
sudo apt install linux-image-generic-hwe-16.04-edge
I am running Linux 4.11.0 and 4.10.15 on my eOS Loki. I am using a customized kernel made by Xanmod. You can visit his webpage here: https://xanmod.org/