Queensland's ongoing state asset sales is expected to fetch some $15 billion to be added on the state government coffers though authorities maintained that the total haul would not be known until the float of QR National has been fully accomplished.

So far, Queensland's state government is in the middle of divesting two major assets with the announcement on Wednesday that the Port of Brisbane was sold for more than $2 billion while QR National has started attracting investors upon it listing on the stock exchange a few weeks ago.

Next to go, according to state officials are the Queensland Motorways, Forestry Plantation Queensland and one more port but state treasurer Andrew Fraser stressed that the QR National float would prove to be the defining point if the targeted revenue of the state government would be realised.

Mr Fraser is optimistic that the sale of the freight services would be an eventual success, leading to the previously forecasted income of $15 billion.

The state opposition, however, is convinced otherwise on matters of the sale forecast as Queensland opposition leader John Paul Langbroek stressed that even if the targeted amount would be achieved, there is no assurance if the state profit would sustain social services and free the government from debt status.

Mr Langbroek added that he is in doubt if Queensland would be able to regain its AAA credit rating as he equally doubt if the forecasted $15 billion profit from the state asset sales would be actually realised.

Also, labour union are bemoaning the three-year guarantee given to Port of Brisbane workers as Maritime Union representative Mick Carr argued that the guarantee would become useless after three years as the new port operators would be given a free hand once the period had lapsed.

The Liberal National Party also scored claims by Brisbane Councillor Campbell Newman that household water costs could be subsidised by proceeds of the asset sales as Mr Langbroek asserted that Mr Newman was not "seriously considering that the proceeds could be applied in the way that he wanted."