I don't believe there's ever been an official explanation of when Apple stopped using the 'i' prefix for new products, but Apple Watch came out after that date.

I don't believe there's ever been an official explanation of when Apple stopped using the 'i' prefix for new products, but Apple Watch came out after that date. My guess - the 'I' prefix was tied to the Digital Hub initiative, where software and devices would tie in via your home computer to share music, home movies, photos, etc. When it became clear that the cloud would replace having all of that maintained on a home computer for most people, adding 'i' as a prefix ended - with iCloud.