SO, as we know the PBE has updated champion bio's, and in Jax's and Zilean's new bio's we learn of a place called Icathia that was desimated by the void, and Kog'maw's passive is called icathian surpirse, so yeah. Theory craft
Kog'maw has always been from the void portal at Icathia.
http://i0.kym-cdn.com/photos/images/newsfeed/000/027/684/1258825362810.gif
Icathia has been a place of Runeterra with strong ties with the Void since season 1.
Just look at this outdated map of the Season 1: http://vignette3.wikia.nocookie.net/leagueoflegends/images/c/cd/MapofValoran.jpg
See? Icathia is there.
And Malzahar literally mentions Icathia: "Icathia beckons." https://vignette.wikia.nocookie.net/leagueoflegends/images/4/43/Malzahar.move1.ogg/revision/latest?cb=20121126173758
In fact; His old lore even mentions Icathia
He ventured into the desert without supplies, drawn by the lure of a specious charm. His destination: a lost civilization to the east, known to ancient texts as Icathia. Few believed such a place ever existed, and those who did were certain that the sands had long since devoured whatever remained.
So.... no, it not a new Region.
Icathia has been a part of the lore, it just wasn't in any of the champion bios before now.
Well yeah,Kog'maw was always from the void and a lot of void creatures originated in Icathia.
Also it isn't sure if Icathia was really destroyed by the void,as Ryzes master devastated the place in Ryzes lore(though we don't know if this destroyed Icathia or not)
