(I think you know about who a Bodhisattva is....)
While a Bodhisattva is in the heavenly realm (Thauthisa) he chooses the
Best time,Best parents,Best cast,Best kingdom,Best country to be born. This is an essential process that all Bodhisattva's go through before being born as a human being.
Here are the reasons why.....
As you know democracy is really new,what existed before is a cast system with nobles and lower casts. Your name sounds Indian so i presume there is no need of explaining the difficulties that a lower cast person will have to go through to get to any higher level in anything. At the age of kings there is no better place to get accepted than being born as a prince and that's why it happened like that in this era.
I have learned that there is an auspicious place on the Human realm that all Bodhisattvas (Who are destined to be A Lord Buddha) reach nirvana and become Lord Buddhas. And this place is the same place every time even after all the destruction that can happen. This time it was India and next time maybe there will be no India, Next time it may be on an island. What we are talking about is a universal position that does not change,its geography,name and other things may change but it will always be the same place in the universe.
Another Buddha can't be born in a particular realm while there is already a previous Buddha's teaching.
(Please not that this is "Theravada Buddhism" and "Mahayana Buddhists" believe in multiple Buddhas in different realms. But even them do not believe that another Buddha can be born in a particular realm while there is already a previous Buddha's teaching.)
Can Lord Buddha be a woman....
No, As Lord Buddha explained a woman who start the life of a Bodhisattva will soon turn into a male in the most nearby life and continue to be male. Because of this reason a Lord Buddha will always be a male.
Please note that this does not mean that a woman can't be a Lord Buddha. What this means is that when she start her practice as a Bodhisattva she will soon get a life as a male and therefore a woman being a lord Buddha does not happen because of this gender change between births.
Can Jesus or any other recent teachers be a Buddha....
No, Because as far as my knowledge goes none of the schools accept that two Lord Buddhas will exist in the same planet at the same time or two teachings would exist at the same time.
Will Buddhism change or modify to suit the time....
No, Because there is one unique thing about Buddhism. And that is....
Akalika = Timeless
As Lord Buddha said there is no need of updating or changing the teaching as it is timeless and complete.
Also Lord Buddha challenged saying that no one can add or remove a single teaching as too much or non worthy.
So there can be differences in
The explaining method
when two Lord Buddhas teach the path. But the core will always be the same. The only difference will be Grammatical and explanatory differences.