The gang over at Vice supposedly have some information on Nintendo's plans to take care of Joy-Con drift issues. Vice says they received an internal memo from a "source familiar with Nintendo's updated customer support documentation." The memo reads as follows.
“Customers will no longer be requested to provide proof of purchase for Joy-Con repairs. Additionally it is not necessary to confirm warranty status. If a customer requests a refund for a previously paid Joy-Con repair [...] confirm the prior repair and then issue a refund.”
Nintendo has been offering this same service since Switch launched, but it was a bit hit or miss when the warranty was up. Now those issues will be fixed regardless of when you bought your system.