Lenovo confirmed Android 6.0 Marshmallow update for some of its popular devices, which includes K3 Note, A7000, A7000 Plus, Vibe S1, and Vibe P1. But unfortunately, you will not get the OTA (over-the-air) update anytime soon on your device. You requisite to wait 7-10 months to get the update.
As per the Lenovo’s Android update tracker (updated on 5 Nov 2015), you have to wait until June/September 2016 to get the Android 6.0 Marshmallow update. K3 Note, A7000 and A7000 Plus users need to wait until September 2016, while Vibe S1 and Vibe P1 users will get the update in June 2016.
Lenovo’s smartphones are budget friendly, but offers great specs and features. The Android 6.0 Marshmallow update definitely will give great experience to Lenovo smartphone users. Android 6.0 core features, such as Doze mode (battery management), personalized app permission, etc. will enhance the use of the smartphone.
However, the long wait for the Marshmallow update is a disappointment. According to the current plan, you have to wait until September 2016 to get the Marshmallow update, which means Google will be on the verge to launch the next Android version (Android N), in all probability. (source 1, 2)