So what has changed in EDA hiring?... Is my wild prediction coming true?... How might Mentor play in all this?...

"... the pool of DECENT candidates is shrinking." I would agree but not because the Big 3 has been adding staff (as well as a few smaller players). I have seen a lot of people leaving the EDA sector for electronics firms (become or return to being EDA customers), Web 2.0 (from start-ups to Google) and management consulting. Higher pay, more opportunity, greater challenges were cited by my contacts. And most of them won't be coming back if you send a recruiter to lure them back (no offence, Mark! But do let us know if you find otherwise).
As for startups, investors (from Angels to VC's) have had their expectations changed due to Web 2.0. In Portland, Oregon a company called Urban Airship was founded at the start of June, 2009 and at the end of July, 2010, they secured $5.4 Million in Series A funding, and just moved into smashing new offices in the Pearl District. Even if someone were willing to do an EDA startup with 'bootstrapping' (self-funding), it would be hard to see it matching the sort of timeline of Urban Airship.

The show of the technology has been recorded for future generations on the basis of social media. Most of the issues of paperhelp.org are involved in the definition of the marks. The turn is fit for the trendsetters. The actual movement is ensured for the role of the scientists for the engineers.