He has a chance, if opinion polls are to be believed, and thanks to the voting system used.
Australian Senators are elected for a term of 6 years, with a half senate election every three years. There are 6 senators for each state. The voting is by a proportional representation variant of the single transferable vote system (called the ‘preferential system’ in Australia).
Minority parties need to get at least 7% of the ‘first preference’ vote and be able to agree to an ‘exchange of preferences’* with other minority parties to have a chance at a seat in the Senate.
Although Assange is domiciled overseas and under threat of arrest, he is still able to run for the Senate. Under section 20 of the constitution, a senator may be dismissed if he is unable to attend for 2 consecutive months and has not been granted leave of absence by the president of the senate. However, under section 15, his place must be filled by another member of his party, conventionally, one who was listed on the ballot paper but who was unelected. Under section 44(ii), he would also lose his seat if sentenced to 12 months or more imprisonment, but only if this was done by an Australian court. In this case again his place would be filled under section 15.
This new party would be best advised to stand a full senate team for each state and look to exchange preferences with other minor parties. The difficulty here is that the Wiki Party voters would probably also be Greens voters and the Greens might be hostile to an exchange.
*A complex series of deals to exchange votes on the ballot paper, but done openly and advertised in campaign literature.