A threat is usually more effective when it looms above the intended victim rather than when it is consummated. The Palestinians have constantly been threatening to take their case to the UN; they have finally done so and the heavens haven't fallen. The Palestinians have applied to the UN Security Council for full UN membership. The request will fail either because they cannot muster the required nine-member majority or, if they do so, then because of the promised US veto.
The next step they can take is to apply to the UN General Assembly requesting that Palestine be upgraded from a non-state entity observer to the status of a state observer; a status enjoyed by the Vatican and, in the past, by Switzerland before it decided to join the UN. If the Palestinians request such an upgrade, their request will be no doubt be approved by an overwhelming majority. It will, however, have no practical effect at the UN since, at the UN General Assembly, the delegation of Palestine already enjoys all the privileges of an observer state.
If the UN General Assembly recognises Palestine as a state it will however lead all other UN-affiliated organisations to accept Palestine as a member. International organisations, other than the UN, do not have a veto system, therefore all that is required for a state to become a member is a vote of a majority of member states. The Palestinians are assured of such a majority in every international organisation.
Whatever the result at the UN, the thorny issues can only be decided by thorough talks.