I was reading an article that states by Nov. 2018, all new apps and new updates for apps on the play store will need to target minsdk level 26, which corresponds to Android 8.0.
Does this mean that my Android 7.0 device will not be able to download and install
new and updated apps on the play store after Nov 2018?
No, that requirement is the target SDK level not the minimum.
Target API level is different from minimum API level. As the name implies, minimum API level is used to declare the lowest version of Android an app supports. The target API level is technically defined as the version of the operating system an app was tested to work with; but in more practical terms, it's used to define a set of behaviors an app expects from the operating system. For example, an app can target API 26 (Android 8.1) while having a minimum API of 14 (Android 4.0).
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