In short OMS was just umbrella for a bunch of services that were sold via common SKU. That is gone now as services are paid per usage just like other Azure services. There are no OMS centric feature as there was never OMS service it was SKU for suite. Because of that I do not think View Designer or any other feature will be deprecated just because the SKU is gone. After all the view designer is fully migrated from Classic OMS portal to Azure Portal and it is part of Log Analytics service. Some features that are not relevant probably will be deprecated (like it happened with My dashboards that was replaced with the more powerful View Designer) but Microsoft hasn't stated that any feature is deprecated because of the SKU being sunset.
Right now there are multiple mechanisms to write custom user interface on top of Azure Monitor Logs (what used to be known as OMS). View Designer is one of them. We are fully committed to provide a mechanism to support writing custom UI over logs. We have not deprecated anything in this area. We are aware to the vast investment that was made in view designer and other tools by our customers and partners and will take it into account in any future decision.