You have no chance of joining the UNSC, since the UN charter requires UNANIMOUS approval from all the P-5 members, before allowing new permanent members.
You can stay as a non-permanent UNSC member though.
Does this mean they will be non permanent members and will leave their seat whereas China will always be there. That is such a shame that a small country by population like UK is also permanent but 1.2 billion Indians are not allowed.