I have written on the article before about the new mobile search engine starting within few months.
But Google announced and postponed "Mobile first index" to the end of this year or the next year 2018.
We can see that this takes time, because this will affect the search engine all around the world, and it should not start in a hurry without high perfection.
One of the reasons that this is difficult to begin is because of the website that is not made by "Responsive design".
Responsive design is the way how to make the website only by one URL and its contents. Only the layout will change to the PC and the smartphone.
But the problem is that not all the websites are Responsive Design. Some websites are separated by the URL for the PC and the smartphone.
Like this, they are using two addresses.
It will appear on a PC website for the above URL and appear on a smartphone website by the bottom URL.
This will change its linked address for the PC and the smartphone, and the unity of the website will be the neck for creating the new search result.
Google suggest using Responsive design, but considering business matters, it would not be a merit for some users, and this will be the dilemma of the search engine side and the creators` side.
Moreover, some people add blog articles to the website but not on the smartphone, and this will conclude to an unmatched page volume that makes differences in PC search result and the smartphone search result.
For Responsive design, page volume is matched with PC and the smartphone so there shouldn`t be any difference.
We have to see carefully how "Mobile first index" will be starting.