There’s a great deal of uncertainty going on around page speed of late, as the new speed Update is scheduled to come in July. Google is expected to introduce a separate page speed score for both Desktop and Mobile.
As people are guessing, Google will introduce only page speed for Mobile, that’s actually not true.
When John Muller from Google was asked about this, he clarified that there will be Desktop page speed for those who are searching on Desktop and those who are searching on Mobile; Google will use the Mobile page speed score of your site.
Speaking at the webmaster hangout at the 37:35 mark, when John asked about such query, he responded “Yeah, yeah. It’s specific to the mobile search results or the desktop search results.”
Here is that video:
If you read the entire process on Google, extremely slow pages would be negatively impacted by this page speed algorithms. If your site is a little bit faster than another page, then it won’t have anything to do with ranking.
See the forum discussion at Google+