Jekyll

As far as I am aware, it differs from Hindu tradition to tradition. There are many different streams of tradition in Hinduism, just as there are in Christianity.

Overall, I think, there is the belief that life is in all living things- when you are reincarnated, you come back into existance as another living thing- an animal, bug, plant, person, etc. I don't believe that people are reincarnated as rocks, but I could be wrong. In Orthadox Hinduism, the end goal is to be reincarnated as a Brahmin male, so that you can break the cycle of reincarnation and reach moksa (sort of like nirvana for buddhists). Your build up of karma determines (in Orthadoxy) into what form of life you are born. This has occasionally lead to social apathy in India, but it is less common today.

As for a cosmic end, there is the understanding that there are not only many worlds but many eras, and when the new era starts again I imagine that reincarnation begins anew.