It seems like the rumors were wrong—there is no Surface Pro 5 coming soon. A Microsoft spokesperson has denied the reports while stating that the current Pro tablet should remain competitive for a few more years.
http://www.notebookcheck.net/Microsoft-shoots-down-rumors-of-an-upcoming-Surface-Pro-5.219628.0.html
Of course, it isn't Pro 5 but Pro S (or 4S) with Win10S
It will be the surface pro they will just stop numbering. Then they don't have to keep refreshing every year.