Unfortunately not at present.
As you might imagine neither Apple or Google provides any practical mechanism to transfer a current user from one platform to the other for a paid app, so that you would be able to the run the app as a licensed user and continue to receive updates.
There is also unfortunately no mechanism under either the App Store or Google Play to offer a discount to a user by way of recognition of a previous purchase on another platform (or for any reason, in fact).
Additionally, each mobile version of TPE is built and maintained separately with its own costs and investment of time.
Please note also that TPE 3D and The Photographer's Transit are only available for iOS at present.
If you have a Skyfire subscription on either Android (through the Skyfire app), or on iOS (through TPE), then you can continue to use the subscription on the other platform via the corresponding app.
We appreciate your understanding.