Re: Sanathana Dharma - will this continue its record of longivity?
I think the other people on the forum can explain better who the Imam Mahdi (pbuh) is. He is the next prophet (?) or as I personally see him, a Spiritual Teacher sent by God who will come to the world soon.
It may surprise Muslims, but Hinduism is probably the one religion which will be able to withstand his coming without disintegrating. Hindus will initially be upset that he is a Muslim and may even reject him in the beginning, but eventually they will recognize him (as they did Shirdi SaiBaba - who dressed as a Muslim and prayed in a mosque) and accept his teachings whatever they are.
Christians will be very upset that he is a Muslim. They will be even more upset that he is senior to Jesus. There will be a major schism between those Christians who accept him and those who do not - many churches will not survive this schism.
There will be a schism in Islam too - Muslims expect a warrior type person who will destroy all the unbelievers and idolators etc, convert everyone to Islam and give preference Muslims (and Arabs in particular). They will be surprised to find a kind, gentle person who accepts all who listen to him and come to him regardless of their religious background. And if he teaches new ideas that are not in the holy Koran, I really wonder how Muslims will react.
It will all be very interesting but also dangerous - there may be a blood bath between those who accept and those who reject his teachings.