Google used to introduce the new Android version  in September , but this year it will introduce Android Nougat in 8/5 with the 8/5 security patch and it won't be available for Nexus 5 users according to Evan Blass and he is Known for his accurate leaks

Android 7.0 releases next month, with the 8/5 security patch. Sorry Nexus 5 owners, no Nougat for you 😢

— Evan Blass (@evleaks) July 30, 2016