According to Christians, God died through Jesus during a Roman crucifixion. According to Hindus, Krishna, an avatar of Vishnu, died from an arrow wound. https://en.wikipedia.org/wiki/Krishna It is not unthinkable for Gods who have incarnated to die.
Regarding the Big Bang, see the debate between William Lane Craig and Quentin Smith, Theism, Atheism, and Big Bang Cosmology. Craig uses the beginning of the universe identified in the Big Bang and the Kalam Cosmological Argument to claim that the universe had a cause outside the universe. He uses Al-Ghazali’s Tahafut Al-Falasifah to show that this cause was an agent who made a choice and because of that a person. So, Big Bang cosmology and belief in God are definitely not completely mutually exclusive. On the contrary, it is lack of belief in God that is challenged by the Big Bang. Smith attempts to defend the position of atheists.
The details of the expansion of the universe are speculative. Gravity waves may be a way to see beyond the cosmic microwave background, so evidence of what actually happened is minimal. John Moffat in Reinventing Gravity provides a survey of his search for a gravitation theory that does not require dark matter and offers a different view of the beginning of the universe. Reading his perspective gives one a sense of what is still unknown about the expansion of the universe.
For a religious explanation why the universe began at all, the answer would be because God as an agent made a choice to create it. Notice, this explanation is one of agent causation rather than event causation. If an agent makes a choice that is the beginning of an explanatory chain of events.
The question whether “there will always be space for religious beliefs” is likely Yes for reasons that have to do with religious belief being innate to our species. The evidence for this innateness of religious belief is surveyed in Justin L. Barrett, Born Believers: The Science of Children’s Religious Belief. The research Barrett presents shows that belief is present in children prior to socialization. Children are not brainwashed nor educated into basic religious beliefs.
However, that is only half of the answer. One can then ask if we could somehow evolve out of this basic belief position. This depends on whether one sees Darwinian evolution as phyletic gradualism or punctuated equilibrium. If phyletic gradualism is true then we could evolve out of the innate position of our species to have religious beliefs although it is not clear how we would do that since social construction did not put those beliefs there in the first place. If punctuated equilibrium is true then we would need a speciation event to occur, in other words, our species would have to split into at least two species one of which no longer supported innate beliefs.