Moving a ripped audiobook to iphone without itunes

With the upcoming deprecation of of iTunes i have a concern.

I listent to audiobooks a lot of on my iPhone - often books I have ripped from cd or downloaded from my library.

The process is to import the folder to the iTunes library - and then adjust the Options metadata to move the files from the music library to the audiobooks library - and then drag the book to my phone. Yes - it is a hassle - but it works.

How will this work when iTunes is deprecated?

I am asking now because i am planning to upgrade my phone to the newest generation, but don't want to lose my access to the books in my audiobooks library. Will I still be able to load ripped audiobooks or downloaded audiobooks to my new phone? Will that ability remain after iTunes goes away?

To me this is an essential set of iPhone/iTunes features. I do not use audible or any similar paid services - since i already have legal copies of the audiobooks in question.

FYI - i use iTunes on a PC.