I have a question here as well:
What is is the percentage of Core developers that needs to accept the proposal submitted as pull request to the Bitcoin Core repository before a BIP is merged or must all core developers / Bitcoin core contributors with the Bitcoin community come to a consensus.
The Bitcoin Core development process does not require a specific percentage of core developers to approve a proposal before it is merged. Instead, it relies on achieving consensus among key developers and the broader community. The decision-making process is collaborative and flexible, with lead developers and maintainers playing a significant role in determining which proposals are accepted and integrated into the codebase.
Secondly is there any possibility that a BIP get merged and isn't part of an upcoming Bitcoin Core release?
Yes, it is possible for a BIP to be merged into the Bitcoin Core repository but not included in an upcoming release. This can occur for various reasons, such as the need for further testing, dependencies on other changes, or prioritization of features. Additionally, some features may be merged as experimental code and not enabled by default in a release, allowing for testing without immediate impact on regular users.