To OP... I wouldn't assume that just yet. I'm sure Kishi has got some new jutsu's planned for her after the Juubi launches his counter attack.
The jutsu doesn't make you old! Tsunade is actually old and when she uses that jutsu she no longer has the chakra to keep herself looking young /facepalm
You sir obviously don't know how genesis rebirth and strength of a hundred work.... Genesis rebirth and its more advanced form work by forcing the cells in wounds to rapidly divide and regenerate repairing the wound at an accelerated rate. This has the down side of causing rapid aging. Cells can only divide so many times before they are killed off by the body to prevent cancer from being a problem.
This is stated multiple times in the Manga as the reason for why Tsunade pretends to be young, because she should look young if not for her using this jutsu. Tsunade would have had to potential to out live everyone if she hadn't used this jutsu. Does Jiraiya look old? They are the same age and he isnt even a Senju....she should look 25 lol.
IE This jutsu will kill you eventually if you rely on it. It will also cause the user to look far older than their true age. IE a twenty year old would look forty or even fifty. The only reason Tsunade isn't dead right now from using the jutsu over her life time is Senju DNA, which allows her some relative leeway with regards to premature aging. So to speak she has more years to spend than say Sakura who will not be able to use that jutsu 1 or 2 times for fear of looking like an old lady. Its that simple.
So unless Kishi ass pulls Sukura a Senju then she quite simply can't even match Tsunade in her own techniques, she might be able to surpass her if she comes up with her own jutsu.
Uzumaki can live to 120 150, using such a dangerous jutsu for them would be far more tenable, for example had anyone other than Nagato used the Gedo mazo against hanzo it would have killed them as it too caused rapid ageing.