Even without negative gearing, you can still deduct the expenses from the rent you earn, and if they exceed the rent, you will be making a loss on the property. The difference if negative gearing is abolished, is that you wouldn't be able to claim a deduction for this loss from your other sources of income.
Perhaps to illustrate this some more, if you earn $15000 in rent, but have $25000 in expenses you are losing $10,000 a year. With negative gearing, you effectively end up losing less than this - $5100 loss if you net income > $180000 per annum, $6100 loss if your net income is between $80-$180K, $6550 loss if your income is in the $37-$80 k bracket ... Of course people hope to make up these losses through capital gains.