It has become a zero-sum game. The pool of customers know it, and play off the majors against each other while making strategic purchases from SME's to keep them alive long enough to be acquired. Things got more complicated over the past 5-7 years as larger electronics firms shrank organically or sold off divisions to smaller firms seeking to grow, so there are more targets to chase but each one slightly smaller than what was typical in the 80's, 90's and early 00's.
Both Mentor and Synopsys are doing well. Mentor in particular is growing since their product quality is best in class. I think the question over the next couple of years is how much business they take away from other EDA companies?