"Classic" lead vocalist Ian Gillan has always been the revolving door of the band...they had David Coverdale for a while, Joe Lynn Turner from Rainbow...Blackmore left after "Stormbringer," came back for "Perfect Strangers," left for good in 1993 after "The Battle Rages On," and for the last few years it's been former Dixie Dregs guitarist Steve Morse.
Jon Lord (keyboards) eventually left too, replaced by session player Don Airey (Ozzy...he wrote the "Mr. Crowley" keyboard intro..Black Sabbath, Jethro Tull, Whitesnake). In 2004 the band is Morse, Airey, Gillan, plus Ian Glover (bass) and Ian Paice (drums) from the "classic" lineup.
But Deep Purple without Richie Blackmore is kinda like Led Zep without Jimmy Page, dontcha think? Who can legitimately leave a band before it's not the band anymore?
I mean, would you buy a Led Zep album if the band consisted of Robert Plant, John Paul Jones, Bonham's kid, and maybe Peter Frampton or someone of his ilk on guitar? Maybe Mick Ralphs from Bad Company or Earl Slick, who did a truckload of albums with Bowie?
The classic, "Made In Japan" (October 1990):
The new one, "Bananas" (October 2003):