- Plans for a seventh installment were first announced in February 2012 when Johnson stated that production on the film would begin after the completion of Fast & Furious 6.
- In April 2013, Wan was announced to direct the film.
- On April 16, 2013, Diesel announced that the sequel would be released on July 11, 2014.
- Principal photography began in early September 2013 and stopped in late November after Walker's death.
- Filming resumed April - July 2014.
Is that unusually early to have nearly completed a summer 2015 movie?
No, not when the movie was originally a 2014 release movie that started shooting the year before. Seems a standard schedule.
The so-called franchise pattern is not some kind of fixed 'thing'. Production and release schedules are subject to many different factors (talents conflicting schedules for example), and such a 'pattern' is not usually one of them.
Don't forget that in 2011, it was reported that 6 and 7 would be shot back to back with a single story running through both films. By 2012 it was confirmed that 7 would not start filming until 6 had been completed, so the planned shooting schedule was very fast in the first place - and had absolutely nothing to do with a '2-year release' schedule.
Wikipedia was used for release/production information.