If she sustains a serious injury, then yes. She's too old to stage another comeback.
If she passes Graf's slam count and is still number 1, then probably (unless she has reached some miraculous goat level and goes after Court, fulfillng nadalagassi's highly improbable prophesy).
I don't see it happening, though. She has said she will play the Olympics. Presumably she would retire at the US Open next year, or go for another year if she feels good. If she's still sitting at 19 or 20, I think she'll retire regardless of ranking.
Number 1 has never been her goal. She wants to win slams. She will enter a slam hobbled, stand on the baseline and take her chances. If she has set a goal for herself (graf or court's record) and she is very close to achieving it, and she believes she can still contend, then I believe she would be willing to bear some painful results to get there. If she thinks her chances are poor, I don't see her sticking around like Venus. She is way too competitive and hates losing too much to do it just for fun. Doubles maybe.
People go on like she is unstoppable but there is something wrong with her, in my opinion. Her serve has forsaken her. It's no longer the goat serve of 2012 and 2013. Why? I don't know. She has recurring back problems, that is a known issue that has affected it in the last few years at times. She had some kind of knee problem recently, which is always a concern given her history. Here is my big worry: she served great in the AO final and she said something that alarmed me after she won. Something about going for it on her serve, no need to save her shoulder. If she has a shoulder problem, look out. She can still win lots of matches without the serve (for example the YEC), but that serve is her "get out of jail free" card. I wonder if she is deliberately playing without her serve to save her shoulder or decrease her reliance on it, or if it has already abandoned her and just shows up once in a while on a good day when all three old age issues are at bay.
