Lightning Web Components have a lot of advantages over the original Lightning Components. LWC are testable, easier to developer, faster to develop and make better use of the browsers and newer JavaScript.
There is no requirement right now to completely rebuild Aura components because Aura and Lightning Web Components can work together. They are completely interoperable.
I don’t think you should be intentionally building Aura (Lightning Components) any more. I haven’t read anything about Aura being deprecated yet, and I don’t expect that we will for a few more years. That being said, I think you should stop.
When will Aura be deprecated?
I think we’re looking at a 5 to 10 year timeline at least. Visualforce isn’t deprecated yet and can work with Aura and Lightning Web Components