There is one possible signal that Jobs wouldn't have chosen to go into philanthropy: He never reinstated Apple's charitable gift-matching program after terminating it during Apple's darkest days. Instead, that turned out to be one of the first things Tim Cook did.
Obviously this is a very limited data point. We know very little about the context around those decisions (e.g. were there external factors that took some time to sort out? did they decide to do it and then deliberately hold back until Tim Cook took over?, etc.). Nevertheless, it is one of the few data points we have on this question.
Gates' parents apparently thought he did not do enough philanthropy earlier on, and Gates was also facing mounting calls from people about it in public long before he started his efforts.
While I don't have much love for either of them, people can and often do change with age. Gates appears to have changed a lot - perhaps Jobs would've eventually too.
Obviously this is a very limited data point. We know very little about the context around those decisions (e.g. were there external factors that took some time to sort out? did they decide to do it and then deliberately hold back until Tim Cook took over?, etc.). Nevertheless, it is one of the few data points we have on this question.