Older than Ohel Sara is the Korban Mincha siddur (which artscroll acknowledges their siddur is based on). these siddurim include tefillos (eg: tefillos for her wedding day) and halachos (eg: kiddush and havdala)geared specifically women.
so, the RCA is putting one on the market. big deal. If they want it to sell, they will promote what makes theirs different than the many versions of the korban mincha siddur, artscrolls many versions of the ohel sara and the other siddurim made for women that are out there. the marketplace will determine its success or failure.