Changing circumstances can cause you to decide to sell your home at ANY time. Stacey is correct in saying you may loose out on that tax credit, but another pitfall, especially if this is not your first home purchase this year is that fact the you will sign in your closing papers that you intend to occupy the subject property as your primary residence and that it is not being purchased as an investment. You will probably sign this statement spelled out in 10 different ways. If you did sell the property right away, and a book thumping, hungry lawyer decides to investigate, they may find this very post (prior to your purchase) and claim that you always intended to purchase the property as an investment, and use this post as evidence that you LIED on your closing papers. This is exactly FRAUD. This particular version of fraud has put many, many people in jail recently.
Not trying to scare you out of making money. Just sayin.