Absolutely. Just add a WooCommerce lead time for the product, and choose whether you want it to appear for In Stock, Out of Stock or On Backorder products. If you choose Out of Stock and/or Backorder, then no lead time will appear for In Stock items. When they go out of stock, the lead time message will appear automatically.
WooCommerce Lead Time also has an option to set a different lead time for each stock status. For example, you might want to set a lead time of "1 working day" for In Stock products, and a lead time of "2 weeks" for On Backorder products. When stock runs out, the lead time message will automatically change so that customers always know what to expect.