Does MTK Android devices get software updates ever? (LG)
Sure - devices from Xiaomi are good examples.

Redmi Note 2, released in 2015, still gets stable and weekly development builds of up-to-date MIUI8. Whether the Android version beneath the UI was updated is a question, but that also stays true for other MIUI devices regardless of the SoCs they're using, and you're not asking about Android version updates exactly, either.