Soon (T103362), the mobile content service will not be using MobileView API for all API queries with the exception of the MainPage. This code will also be redundant upon completion of T32405.
When the iOS app has switched over to the mobile content service there will be no need for the Wikimedia Foundation to support the MobileView API.
Of course deprecating should be done carefully - there may be other consumers of this API, but we should explore who they are and how we can get them using MCS.
Note: The MobileFormatter will continue to exist for MediaWiki mobile web views. The MobileView API actually has a lot of logic that is not shared by the MobileFormatter.