We posted back in the fall that Sigma had halted production indefinitely of the relatively new 24-105 f/4 DG OS lens. We're now told that the lens is in fact discontinued and production has been halted forever.
There was no word as to why it was discontinued, I can only assume the market for a 24-105 on the Canon side is extremely saturated and that the Sigma wasn't a big enough leap forward in terms of optical quality to purchase over the “kit” lens from Canon. There's also a possibility the cost of production was too high to keep the price competitive.
We're still waiting on an official release about this from Sigma.