Yes, we are working on a Sketch version of the stencils that will come with the new Fiori 3 / Quartz Light design. It will be made available externally when we next update the SAP Fiori Design Guidelines. This is currently planned for February/March 2020.
Whether you go for Axure RP or Sketch depends on your requirements. For example, Sketch is only for Mac, while Axure RP can be used on both Mac and Windows. We plan to continue providing SAP Fiori stencils for both in the foreseeable future.