Postal rates are going up to 44¢ for regular first class letters. Thats a 2¢ increase. If you know you'll need some stamps next year then right now is a good time to go buy some Forever stamps. You could get a sheet of the Forever stamps today for 42¢ and then next week they'll be worth 44¢. You can buy Forever stamps online at the USPS site or at various local retailers.
I wouldn't go out of my way to buy a big pile of stamps. But if you know you'll be using a few within the next year then it could save you a few bucks to lock in the 42¢ cost before the rate goes up on Monday.
Image from USPS.gov