In his April 29 review of Fast Five for the Chicago Sun-Times, Roger Ebert wrote:
The "F&F" titles got confusing with the unrelated "Fast and Furious: Tokyo Drift" and John Singleton's "2 Fast 2 Furious," which is why, I suppose, "Fast Five" drops the "furious." But it isn't technically the fifth "F&F" unless you count the outliers. So I don't know what "Five" refers to. That doesn't bother me.
Maybe the titles did get confusing since only two in the decade-old series employ numbers—it doesn't help that the first and fourth entries essentially have the same title—but if Ebert had checked his facts he wouldn't be so confused. (Perhaps he should have visited Mulberry Panda 96 for a refresher course on the highly profitable street-racing saga.)
The series' second entry, 2 Fast 2 Furious (2003), stars Paul Walker, who was also in the first film, The Fast and the Furious (2001); his costar in the sequel was Tyrese Gibson, who returns in Fast Five. Vin Diesel skipped 2 Fast 2 Furious but showed up in a cameo at the end of 2006's The Fast and the Furious: Tokyo Drift—which didn't feature any other characters from the first two films—then returned to the series full-time, along with Walker, for Fast & Furious in '09.
See, Roger? They're all connected, and Fast Five really is the series' fifth installment, even if it sounds more like the name of a lotto game than a movie. And since it had an $86 million opening weekend, it's a safe bet that "Grandmaster Fast and the Furious Six" will be crashing into a theater near you sometime in 2013.