Fact is wrestling has still been MainStream since 2002, Rock's movie career took off, we've seen national advertising campaigns for John Cena, HHH, & Hogan among others, Ric Flair & Mick Foley had books in The Top 5 in sales on The NY Times Best Selling Charts, and every year there is significant attention in newspapers and news shows paid (at least in passing) to WrestleMania, especially this past year with Rock's return. Certainly Jerry Lawler's heart attack made major national headlines. Ive seen Flair profiled on the CBS Evening news prior to WrestleMania 25. Overall interest in the product maybe down, but the wrestling industry and it's biggest stars are still considered main stream celebrities. Ive also seen Foley get national news coverage over his political support, and Flair has been on TV news shows campaigning for Presidential Candidates in 1992 and 2004 that I saw. Stacey Kiebler was on Dancing With The Stars.
Now I think this was more prevalent in 96-99, other than Hogan in 94 before The Bash At The Beach I have very little memory of any wrestlers doing mainstream news or entertainment shows after the very late 80s (Anyone remember Randy Savage as WWE Champion on Arsenio Hall in 88 ?). During that 96-99 time frame I remember a lot of WCW guys like Nash & DDP on MTV, the whole Hogan-Bischoff Tonight Show, the Celebrity Death Match parodies, Steve Austin moving into mainstream acting on network TV shows like Nash Bridges, The Divas were getting much publicity for their Playboy shoots (now it seems their only publicity is for getting fired or going to re hab), and Regis Philbin always had time for wrestlers from both companies including Rock, Hogan, Flair, Sting, and others. The Brett Hart documentary on A&E was a major accomplishment during this time, as was their profile of Hogan for their "A&E Biography" series, although that may have been post 2000.
Fact is wrestling and it's biggest stars have been mainstream for years, right now we are in a downturn in terms of popularity. Still, top stars like Cena are attractive for comercials, kid movies, etc.