OP, how do you think childless people deal with old age? If your mother hadn't had you, and your siblings had remained uninvolved, she would have had some form of paid-for care. Which might not have been ideal, but then neither is being cared for by children, always. My mother, despite having two richer siblings with fewer dependants, looked after her elderly mother for years in our tiny, overcrowded house, and it was awful - my sister and I entered our teens sharing a bed with an elderly incontinent woman who was never very nice to us, and then my father spent three years sleeping on the sofa while my mother shared a bed with her - and she still ended up in a home.
I can see that looking after your mother as she declined has had a traumatising impact on you, and I'm sorry. But I don't think fixating on something that is years off, if it happens - you could be hit by the proverbial boys - is going to do anything other than make you miserable and have a negative impact on your rel with your sons.
It already sounds as if you half-resent them in advance because you don't think they are going to look after you the way your imaginary daughter would, in your fantasy. If she lived down the road rather than in Rio or Cape Town or Athens. If she didn't work 80 hour weeks with a lengthy commute. If she wasn't a single mother with a profoundly disabled child. If she didn't have a serious disability herself. If she behaved like you did towards your mother, which is the basis for your fantasy.
You'll think I'm being brutal, but I think it might help to recognise that your caring daughter is a fantasy. If your daughter was real, and your relationship was as problematic as real relationships are, and she decided to go and live in Alaska, would you be as scared and resentful as you are at the future as you imagine it with your sons?
And I do think you have some essentialist ideas about gender. I am careerist. I work long hours at a job that is consumingly important to me, as does my husband, and I certainly am not more prone to noting missing toilet paper or malfunctioning appliances than he is. The house could go to hell in a handcart before I would notice in a busy period. I am a real woman, not a fantasy daughter. I'm sure other women function differently, but I'm just pointing out that your daughter might be like me, living her entire adult life in a different country, completely undomestic, and, although I have a warm relationship with my mother and we see each other as often as can be arranged, I have - and nor do my two sisters - no plans to move to my home country again.