Jerry Shen, Asus CEO, discussed the cases for the Zenfone 3 at the recent investors conference. He used the word “transparent” which quite possibly means a clear plastic shell case that will not cover up the design and look of the Zenfone 3.
During the same question period, Shen also indicated that some of the more expensive Zenfone 3 products, they will include a case. So to us, this would include phones like the Zenfone 3 Ultra and Zenfone 3 Deluxe. Sounds good but we should definitely wait to see if Asus includes cases in the same box. They still need to make money afterall.
for high end products, phones will come with cases
for mainstream products, cases will have to be bought separately
Asus has bundled their ZenPad Theatre with a case and in some countries the ZenPad S 8.0 (Z580CA) was bundled with the Clutch Case. Thus we have no reason to doubt the information that premium Zenfone 3 phones will have a case included. It is most likely to vary from country to country however.