Chaos and "Order" (apparently the term was Law, I was a bit off, but that's what I remember) were specific opposed forces in old WHFB, and I think they are in AoS. The term was still Chaos Gods of Law, funnily enough, but there was an idea of "Good" counters to the Chaos Gods. That idea has kind of died-off over the years, and while I am pretty sure it was never outright denied, like many other things, and there are still some small references there and there, it's not really a thing anymore. As far as WH40K approach, presumably Emperor, in his "God" state, when and if he achieves that, would represent a Chaos Gods of Law. If it were anything like old WHFB though, there wouldn't be one specific Chaos God of Order, but a whole array, in which case Emperor would just be the newest addition. While old Eldar gods could be shoe-horned in that role, as at least some of them are kind of a "better" version of Chaos Gods, I don't think 40k was ever created with the idea of Chaos Gods of Law being a thing, since it turned to just Chaos Gods having more of a positive side, at least in theory.
Of course Chaos isn't the neutral and natural state of Galaxy. Before the whole War in Heaven and Enslavers and all other random Warp beings, Warp was stable and while I don't think it was particularly ordered, it was there. When Old Ones came by, they started introducing Order, in form of, for example, Webway, which is like a stable-ish Warp. War in Heaven destabilized it towards Chaos, and ultimately it resulted in a snowball effect. This is why I would never consider True Chaos anything close to neutrality, and (seriously, the term is fucking retarded and people get wrong ideas) the same applies to Chaos Gods of Law, or, just generally, Order. However since presumed deities that represent Law and Order, instead of Chaos, still take their power from The Immaterium, which the common name (or rather, denonym?) for is Chaos (thus, Chaos Gods of Law, not because they're chaotic, but because they come from the same place as Chaos), then an amalgamation of that would mean that it'd be Chaos (or rather Immaterium) Undivided in the form where it also takes into account Lawful deities. So, surely, that would actually put the ending result as True Neutral, as they should balance each other out.
However, since the Chaos Gods of Law are not anything that'd be canonical right now (though their existence or perhaps, future existence isn't ruled out), that means there are only chaotic Chaos deities, and Emperor isn't actually a Chaos God of Law, just an interchangeable version of some other Chaos Gods and Eldar Gods are just some weird facets of Chaos Gods, and Gork and Morks are, well, I don't know, whatever, Orky versions of some weird Khorne/Tzzentchian gay pairing, it ends up as only Chaos, which is certainly not neutral in that state, resulting in just a Chaos Warband that just believes in Chaos in an extremely Undivided fashion where they just consider every deity some version of Chaotic deities, adding to each other, even taking into account stupid shit like Void Dragon which clearly is not an actual God in the same sense Chaos Gods are, to which title Emperor comes the closest out of all not-Chaos God beings right now.
This is fucking medieval scholasticism at it's most absurd. How many Warp Storms can Emperor fit on a head of a needle?