I don't think there is reason to worry on this score. Neither does Andrew Sullivan of The Atlantic. He cites two key recent events as reasons:
1) The Bush administration's chief prosecutor at Gitmo, Susan Crawford, has herself conceded that torture did indeed take place in that camp, and specifically against Qahtani, the prisoner whose torture was personally monitored by Bush, Cheney and Rumsfeld, and whose torture log is in the public domain.
2) The second big thing is that the perpetrators of war crimes are no longer in power. I predict that as fear of administrative reprisal ebbs, more and more whistle-blowers will come forward with evidence of what was done under Bush and Cheney, in defiance of domestic and international law.
Obama's relative silence on this issue is reminiscent of his handling of hot-button issues during the campaign when he kept quiet and allowed others to make controversial points for him. Rep. John Conyers (D-MI) and the House Judiciary Committee released a 500 page report earlier this month that advocated the establishment of a bi-partisan commission and selection of a special prosecutor to investigate possible crimes committed by Bush officials in the War on Terror. Eric Holder, Obama's nominee for Attorney General, has said publicly that "waterboarding is torture." Other key players in the new Justice Department have similar stances on torture as well as the Bush administration's dubious claim of a legal mandate for such behavior.
Look for Obama to respond to an outcry from Congress and the public by instructing his Justice Department to investigate in a scrupulously legal manner.
UPDATE: Mark Kleiman speculates on how this will play out in The Reality Based Community.
Holder will order an investigation, the investigation will come back with the conclusion that there is enough evidence to convict X, Y, and Z (where the value of X might well be "Cheney") of conspiracy to torture, Holder will reluctantly say that the law must take its course, because the treaty strips him of prosecutorial discretion if the only grounds for not prosecuting are policy and politics rather than doubt about guilt or about the evidence to prove it, Obama will even more reluctantly say that, much as he'd prefer to look forward rather than back, he swore to take care that the laws be faithfully executed and it would be inappropriate for him to interfere with justice.--Ballard Burgher