This is just my ideas, but from what I have seen this is the most likely way expansions and patches will work with free to play.
Patches:
Patches will be one or two piece(s) of content only, like a new operation or warzone. The base patch will be free, but the new content will run for around 1 dollar to 5 dollars (depending on size of content, how many pieces etc.) for free to players, and free for subscribers
Example: Terror from beyond
Mini-expansions
Mini-expansions will include one major new piece of content, most likely a planet, new gear, and a level cap increase of 5. These would cost 5-15 dollars for free to players, and be free to 5 dollars for subscribers
Example: Makeb
Expansions
Expansions will add a whole new story chapter including 2 to 4 new planets, an operation and warzone, new gear, a level cap increase of 10-20, and add or enhance a gameplay element.
These would cost 30-40 dollars.
Tell me what you think about my theory, and how you think content will be structured.