Buy house with market Crashing?

I made an offer on a house that was accepted but I have not yet signed a contract. With the market in both the US and international looking like it may be crashing how will this effect housing prices. I am nervous because I will still have to sell my current house and don't want to be stuck upside down in a new house.
Added (1). Edit: Thanks for the responses. To address some of the answers I have enough saved to make a 20% down payment and support both mortgages for over a year. I also will be buying this in Long Island near NYC in an upscale community and my worries is mostly that most of the people that are buying in that area either work on wall street and this may effect prices.

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