I answered this before. If you go to this page: INTEL-SA-00088 Schedule for Intel Desktop Boards, while it is true that they have not published a schedule as yet, if you click on the See All in the Find support for related products section, you will see what I interpret to be the full list of Intel Desktop Board products that they intend to release updates for. As you can see, this encompasses practically all of the 5 through 8 Series Intel Desktop Boards (coinciding with the 1st through 4th Generation Intel Core processors).
As the original and Feb. 20th update for the INTEL-SA-00088 Advisory has detailed, Intel's highest priority is to deliver updates for the processors produced over the past five years. Work on older processors will not begin until this goal has been met. Once this work is begun and schedules for the delivery of the microcode updates for these older processors have been established, they will then be able to assess when the updates can be delivered for the Desktop Boards.
Sorry I can't do any better than this. It is what it is.
We will offer additional microcode updates from Intel as they become available to Microsoft.
So yes, Microsoft will deliver CPU microcode updates if hw vendors are not interested for older devices.