The MobileView API was originally made for apps. Now that the MCS is being used (T103362),, its value is questionable given its maintenance cost. On the long term it seems like a good idea strategically to deprecate it.
The MobileView API is only used for the MainPage. This code will also be redundant upon completion of T32405.
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.
= Developer note
 The TalkOverlay currently uses the MobileView API. There is no need for it to use that. Use the parse API instead e.g.
https://en.wikipedia.org/wiki/Special:ApiSandbox#action=parse&format=json&page=San_Francisco&prop=sections%7Ctext and remove the Page::getPage method.
= Open questions =
 The PageGateway uses the mobileview api to get and allow lazy loaded references and to get pages. How could this work without the MobileView API? Can it work? What are alternative options?
= Time line=
If all goes to plan all Wikimedia apps will be off the API come February of 2020.
After that, we'll wait until the usage is low enough (in apps) to warrant its removal.
So theoretically the API will be around till at least the end of 2020