Riot announced today that the 1v1 and 2v2 map "Magma Chamber" had officially been canceled and all development on the project halted. That comes despite the initial announcement that the mode would be available for all the play prior to the start of Season 4 (starting right around now).
The cancelation comes on the back of several findings, according to Riot. Recently they launched the temporary Showdown match-type which allowed players to battle 1v1/2v2 on the Howling Abyss map. Apparently pros and testers found this map much preferable to the Magma Chamber. More of an issue, however, was that after an initial burst of activity it dropped to less than 1% of gameplay minutes.
Combine the above with the fact that the initial Magma Chamber map was thrown together hastily and extremely unoptimized and you get a recipe for Riot cancelation. Though let's be honest here, the only reason it's not being made is because Riot isn't interested in finishing it.
It's a simple thing to release a map with no ladder, no leagues, no ranked mode, and only advertise it for a week before letting it quickly fade away. Of course it's only going to last a week of high activity. Why would players care if Riot doesn't show that they care either?
If Riot has any intention of pursuing another 1v1 or 2v2 map for League of Legends of a different form they gave no hint. Ultimately another disappointing revelation for League of Legends fans. At least we have the LCS starting today, I suppose.