Yes, Lineage OS team has posted the initial manifest files on their Github for Lineage OS 16 based on Android Pie. Although there is no ETA (Estimated time of arrival) for this ROM yet! So stay tuned here. We can expect an unofficial version of Lineage OS 16 for any device before the official.If stock ROM is here, can custom ROM be far behind..?! Android P or Android 9.0 Pie has finally released for various popular devices and OEMs. It brings a lot of newer features and improves the existing ones.
Now, if we sit looking at Android’s history, every stock ROM makes way for an efficient custom ROM, thanks to the open source nature of Android. There is a great demand for custom ROMs because for the flexibility it brings. and Lineage OS is one of the foremost custom ROMs to exist in the scene. It brought its own iteration based on Android Oreo which was quite popular and well appreciated. Now Lineage is forraying its domain into Android Pie. This means the work on Lineage OS 16 based on Android Pie has now started.
As much popularity stock ROM has, that much of a necessity custom ROM becomes for certain users. Stock ROM comes with certain limitations which the custom ROM overcomes. Every feature in a custom ROM has great scope of customization which further enhances the efficiency of the OS. The intelligent minds behind Lineage have posted the manifest files for LineageOS 16 based on Android Pie on Github. However, there is no update on the actual fullscale release of the custom ROM based on new Android OS.
Just to revisit, we know Android Pie brings new features such as Swipe Gesture navigation, Rotation suggestion, Adaptive Battery, Adaptive Brightness, App actions, Text selection, revamp to Quick Settings and Volume section, Smart replies, and Notification Panel. There is the new Digital Wellbeing feature for enabling an efficient and controlled use of smartphones. So, in the Lineage OS 16, we can expect these features as well that too with more efficiency.

How do you know that it will be available on the A5 2017?
Who told you?