I view Siming as, more or less. retired from pool. It's very unlikely that, if she returned to pool, she'd regain the #1 spot.
Centeno and Chou are at the top of the women's game right now, and Han Yu is, perhaps, third. After that, Jasmin and Seo are probably next in the pecking order, and after them, it's hard to choose between Wei, Rubilen Amit, Shasha Liu, Kelly Fisher and Kristina Tkach.
Those are my top ten, but the possible return of Xiaofang Fu to competition could possibly shake things up at the top.