It’s a neat idea, although nothing really needs to be done to implement this. Each species already has a permanent URL so you only need to display that as a QR code.
For example, the URL for the page about English oak is https://www.inaturalist.org/taxa/56133-Quercus-robur so you just need to render this as a QR code (using any of a thousand free apps or online convertors) and voila you have the scannable link:
I suppose if iNat could implement directly downloadable QR codes from within the site, perhaps integrating their logo, but other than that it’s already quick and easy to do what you want.