A MK2 lower that is fully ambidextrous would be a logical next step (especially now that companies like Daniel Defense are offering them), but I dunno that it's even in the works right now. If it is, BCM hasn't been teasing it on IG yet, the way that they did with the MK2 upper receiver (for over two years) or any of the latest accessories that became available this fall.
I actually find it weird that we now have a MK2 upper, but not a lower, at this point. It is more common for AR makers to prioritize introducing ambi lowers before they think about doing ambi uppers (if they offer the latter at all), but BCM has done the opposite.