The Federal Government is the overriding authority in Australia that determines if the Northern Territory (or any other territory) were to become a state.
Australia's constitution of 1901 did (and does) allow for the admission of new states into Australia. Section 121 of the constitution states that all that is required for a new state (or, in this case, for a territory to be declared a state) is for the Federal Parliament to agree. This even means that the Parliament could admit the Northern Territory as a state whether or not the NT agreed to it.
It was a territory.
It's a state, not a territory
No, it is a Territory. A territory may aspire to become a state but it depends on many factors.
Hawaii
ohio
michigan
A territory can become a US state through an act of Congress. The territory must first apply for statehood and then go through a process to draft a state constitution. If Congress approves the statehood petition and constitution, the territory can be admitted as a new state.
How_did_that_territory_become_a_state_so_quickly
admit
Kentucky
It had to have 60,000 free settlers. Then It asked Congress to become a state.
There is no specific limit required for either the Northern territory or the Australian Capital Territory to become a state. For either territory to become a state would be a fairly straightforward matter. Australia's constitution of 1901 did (and does) allow for the admission of new states into Australia. Section 121 of the constitution states that all that is required for a new state (or, in this case, for a territory to be declared a state) is for the Federal Parliament to agree. This even means that the Parliament could admit the Northern Territory as a state whether or not the NT agreed to it.