Like Rainbow said, baby steps. What you saw on Raw last night were all the active women who make up the current main roster: Charlotte, Sasha, Becky, Tamina, Naomi, Paige, Summer Rae, Lana, Natalya, Eva Marie and Emma. Of those women, the ones that most fans have either no real interest in or haven't proven that they can wrestle are Summer Rae, Lana, Eva Marie and Tamina. So that leaves about eight women who most would view as viable candidates for Charlotte's WWE Women's Championship, in which one or possibly two will be vying for at any given time; as a result, you'd have between five or six women to be in contention for a WWE Women's Tag Team Championship. At this point in time, WWE having a women's tag championship serves as much purpose as TNA having a women's tag championship a few years back: title belts that exist for no reason than for someone to carry them around.
There's not really enough viable women on the roster right not to warrant having a separate tag team division. If WWE was to add another eight or ten women to the main roster, women who have the goods aside from being pleasing to look at, then they'd have enough to possibly warrant discussions for a tag team division for the women. However, that's probably not too likely to happen for several years yet as maybe there might be two or three new women, at most, who head to the main roster between now and the end of 2016.
I'm of the opinion that if WWE was considering a new championship for the women, one that has viability that potentially outweighs a tag team championship at this time is some sort of secondary title for the women so that the women who aren't challenging for the WWE Women's Championship may have something to aim for.