Actually 15 Pro has the A17 “Pro” SoC, while the regular 15 uses the last gen A16 Bionic (Bionic being the regular version). We don’t know whether the next regular iPhone will get the last-gen A17 Pro (which would be a little confusing), or a “last-gen-but-new” A17 Bionic or if they’ll go with 18 Bionic + Pro.