MS has reverted instead to a bi-annual feature update instead, around March and September. They can set previous versions to "end of life" much sooner. This kind of forces all home users to have pretty much the same version of Windows, which is easier to support, rather than having countless different users on different versions. It makes sense from their perspective, but it hasn't been without its problems in the past.
Critical and security patches I believe are still released on the second Tuesday of each month, but I may stand corrected on this.