Most women in the WWE retire at a younger age than the men. The oldest active women in the WWE right now are Tamina (39), Mickie James (37), and Asuka and Natalya are both 35. Can you see any women on the roster wrestling into their 40s or 50s?
Its definitely between Alexa Bliss and Sasha, and maybe some younger talent from NXT.
Anyone who is over 30 right now (Becky, Asuka, etc) have no chance. Charlotte maybe but only because of her name and the preferential treatment, she might avoid WWE's apparent dislike of older women on their roster.
I'd be surprised if Charlotte doesn't wrestle past 40 as a part timer. Becky said a while ago she has another decade left. Sasha will probably be around for a long time if able but she bumps pretty hard. Her body could break down sooner than it should if she's not careful.
I doubt any of the older women will stick around that much longer. Mickie James has been wrestling for nearly 20 years and this current run really looks like a veteran putting over the next generation before retiring. It's hard to guess with Asuka. AFAIK she's went her entire career without a single injury, so she could have a lot left from a physical standpoint. I just don't see WWE keeping her around for more than a couple of years though.
Alicia Fox and Natalya are 10 years in and it doesnt look like they are leaving anytime soon. Both Sasha and Charlotte have stated they want children so I dont see them lasting as long as Nattie and Fox