During a C-SPAN interview taped Friday, National Republican Senatorial Committee chairman John Cornyn claimed "a lot of people are looking back with more fondness on President Bush's administration" (video):
Cornyn also defended Democrats' attempts to make former President Bush an issue in the 2010 election. "I think President Bush's stock has gone up a lot since he left office," Cornyn said, citing Bush's response to Sept. 11. "I think a lot of people are looking back with more fondness on President Bush's administration, and I think history will treat him well."
While conservatives may be "looking back with more fondness on President Bush's administration," there's no evidence of a general pro-Bush shift in public opinion. Here's a chart showing the proportion of the public that reports having a favorable or positive opinion of Bush since January 2009:
The trendline is essentially flat. Given the state of the economy, for which many Americans hold Bush responsible*, I wouldn't expect his ratings to improve any time soon.
* A June NBC/Wall Street Journal poll found (PDF) that 40% of Americans think Bush is "solely responsible" or "mainly responsible" for the state of the economy and an additional 46% think he is "only somewhat responsible."