Below is the email that was sent out from Salesforce:
As an admin of a Salesforce org, we want to notify you of an important change to the support of Salesforce1 for Android, which your organization has used in the last month.
What is changing?
With our Winter ‘16 release*, Salesforce will no longer support the Android 4.3 operating system (OS) or below for the Salesforce1 application. While you will still be able to use those operating systems with your current version of Salesforce1, support for technical or product issues will no longer be provided by Salesforce and no further development will take place. This means that users will only get Salesforce1 upgrades if they are using Android OS 4.4 or higher, which is a requirement for the latest version of Salesforce1. As a reminder, Android tablets will remain unsupported.
*Currently targeted for October 2015; date subject to change
Why are you doing this?
As we evaluate which operating systems to support for Salesforce1, we consider which ones will give our customers the best experience. Those assessments allow us to focus our development efforts on features and capabilities that will add the most customer value. To that end, upgrades coming in the Winter ’16 release will require Android OS 4.4 and higher.