DETROIT  With a lifeline from the White House, General Motors and Chrysler will survive for the next few months while they revamp.

But will they thrive again?

The plans from the car companies offer little in terms of fresh ideas. Instead, they are focused more on slow-selling models, persuading G.M.’s debt holders to accept stock and getting union wages more in line with those paid by foreign brands in the United States.

Such moves are certainly necessary in the short term, but no company can keep cutting its way to prosperity. Even President-elect Barack Obama said Friday that Detroit automakers should not “squander the chance” to change their management practices.

To be sure, it takes years and enormous investments to develop new vehicles, and much of Detroit’s focus throughout this decade has been on shedding workers and closing plants in response to its shrinking market share.