[Android General] Tzul:
Because SuperSU 2.66 is obsolete. The current version is 2.67. ;)

Joking aside, the latest stable version still is 2.46, and I actually considered integrating this one into TWRP. But then I chose 2.52. The reason is that 2.52 worked perfectly in my tests, and is the latest beta version before "systemless root" was introduced.

Systemless root is a neat feature, but still experimental, and mainly needed for Android 6 Marshmallow. Instead of installing itself in the /system partition, SuperSU injects itself somehow into the boot partition, and uses advanced trickery to make the su binary appear in /system/xbin/su, where apps expect it, even though it's not really there. Hence "systemless".

Just look at the changelog, most changes since 2.52 deal with systemless, and we don't need that.

I don't have time to tackle TWRP 3 at the moment, sorry. A few pages back, lion567 uploaded a version, but it didn't work for the A10-70F and also has the same bug that some of our previous builds suffered from: incomplete backups of /system and /data.

You mean the latest "A10-70L_S000115_160119_ROW to A10-70L_S000116_160129_ROW" incremental update? I just saw it earlier today. Unfortunately no new update for the A10-70F yet. Since Lenovo doesn't release changelogs, we don't really know what's changed. You can look inside the update zip, but that doesn't really help.

I don't know, I haven't tested OTA updates with TWRP or heard reports from someone who did. I think it should be possible to install "type 1" updates. They basically include an entire new /system partition image, plus new boot image and some other stuff like tee/trustzone. So, they should just overwrite your current /system partition, and therefore wipe out SuperSU. But you can just reinstall that afterwards...

Then there are "type 0" updates, like the latest A10-70L one mentioned above. They are incremental/differential in nature, meaning they don't contain complete partitions or files, but only patches. And they rigorously verify checksums when they apply those patches. They might or might not work... with systemless SuperSU they definitely wouldn't work, because then the checksum verification of the boot partition would fail. ;)

[MENTION=2895182]clsA[/MENTION] Have you actually tried it? This is the update script for the latest A10-70F_S000121_151222_ROW "type 1" update, for example:

getprop("ro.product.device") == "A10-70F" || abort("This package is for \"A10-70F\" devices; this is a \"" + getprop("ro.product.device") + "\".");
show_progress(0.750000, 0);
block_image_update("system", package_extract_file("system.transfer.list"), "system.new.dat", "system.patch.dat");
show_progress(0.050000, 5);
assert(package_extract_file("boot.img", "/tmp/boot.img"),
write_raw_image("/tmp/boot.img", "bootimg"),
delete("/tmp/boot.img"));
assert(package_extract_file("mobicore.bin", "/tmp/tee1.img"),
write_raw_image("/tmp/tee1.img", "tee1"),
delete("/tmp/tee1.img"));
show_progress(0.200000, 10);

This script is very simple and doesn't perform any checks concerning root or other modifications. So, unless the update binary itself does integrity checks, I see no reason why this wouldn't work in TWRP and with a rooted system.