The revised 1Q GDP figures to be released next week, will likely support the sense of optimism that pervades the market, according to a report by MarketWatch.

Economists expect the gross domestic product to be revised up to 0.9% in the first quarter, from the initial estimate of 0.6% when the government releases the data on Thursday morning.

However, many economists aren’t so sure that the ailing US economy is out of the woods yet. They argue that the toughest times may even come next year until the impact of the economic stimulus wears off.

“The cold shower will come when they realize [the pop] from the stimulus was just temporary and there are a lot of big fundamental problems and growth is just going to fade away in the fourth quarter and first quarter of next year,” says Nigel Gault, chief US economist at Global Insight, quoted in the report.

“The economy needs more than a jump start to get it going. The engine has too many problems to kick into gear until the middle of next year at the earliest.

William Patalon III says the bearish case for the US economy is strong and has just got stronger following a prediction of a major lending pullback by Oppenheimer & Co analyst Meredith Whitney.

“Whitney’s reputation has soared like a skyrocket since she made her bearish — but highly prescient — call on the banking sector, including Citigroup.

“Now she’s back. And her outlook for the financial sector is actually worse. Whitney is now predicting that the banking-sector’s financial crisis will extend well into next year. If not beyond.

And that’s not even the bad news.

Whitney now says the worst may be yet to come. The banking-sector financial crisis will last at least until the end of next year, and may actually stretch well past that. And that could lead to a major U.S. downturn.

“’We believe the credit crisis is far from over,’ Whitney wrote in a research report last week. ‘In fact, we believe what lies ahead will be worse than what is behind us.’

The so-called ‘first wave’ of the credit crisis hit banks’ trading books. But the second lightning strike will hit lenders where it hurts the most — right in their lending businesses. If she’s right, the impact on the economy will be devastating.”