I bought EQ8 a few weeks ago and asked customer service if EQ9 was on the horizon before I spent the money for 8. The CSR I spoke to said 9 is not even in development yet.
I upgraded from 4 to 6, and skipped 5 completely. I don't know about 5, but 4 had a major problem with it. When it calculated the fabric yardage for long strips like borders, it assumed that each border was one piece and that you could only get one strip from a length of fabric. So for a 2-inch border on a lap quilt that measures 45"x60", it said you needed 5 7/8 yards! You only need 5 WOF strips for that size, 12 1/2 inches if you cut them at 2 1/2.
I really liked 7, but it wasn't compatible with Windows 10.