Reporting to the board on his experience appearing before the parliamentary health select committee this week, Mr Millar said he was asked when he thought the two boards would be merged.
He had explained that it was not "our decision" , but it was "not that far away".
In recent years the boards have increased their collaboration.
They share senior managers, including the chief executive, have some shared clinical services with more being planned, and two of their advisory committees have membership in common.
At the select committee meeting, the measures taken by the board following the discovery of the $16.9 million fraud were also discussed.
Chief executive Brian Rousseau said it was a constructive meeting with an absence of "sniping", which he had experienced at previous select committee hearings.
The committee is chaired by National's Paul Hutchinson, with Ruth Dyson (Labour) as deputy chairwoman, and the members include southern National MPs Michael Woodhouse (list), from Dunedin, and Eric Roy (Invercargill).
