Apple is elevating Design not just Jony.
Design is one of the most important ways we communicate with our customers, and our reputation for world-class design differentiates Apple from every other company in the world. – Tim Cook to employees
This will likely be a permanent position just like CEO, CFO.
Let’s not underestimate Howarth and Dye. Howarth has been with Apple for 20 years and Dye for 9. One theory I have as to why they waited till now was to see how Dye performed with shipping a completely new product, Watch, because although Dye joined Apple in 2006, it appears that he wasn’t brought in on iPhone/iOS until iOS 7.