There are many factors to consider when selling land. Federal capital gains taxes are now at an all-time low of 15%, down from 20% to 30%. Land prices are at all-time highs. Farm income is expected to be at an all-time high due to high grain prices and big crop insurance payouts. Based on that, land prices should continue to rise, but our do-nothing congress has not passed a farm bill yet, that could affect future farm incomes and land prices.
Your best choice is to talk to a tax accountant from your area to find out what your state and local taxes really are. Don't believe everything you hear in the cafe, bar or internet, take the time to talk to a professional.