This website post sates that in March of 2011 the Sims Medieval will be released, a new game DarkSpore and a new Sims 3 stuff pack, Outdoor Living Stuff will be arriving February 1st. It was leaked when someone scanned the GameStop game arrival list, and posted the pictures online.
Also the Sims 3 for Nintendo 3DS will be arriving the same day as The Sims Medieval. And the next Sims 3 expansion pack is rumored to be released around May 10th of next year. So let's just focus on the fact there will be another expansion pack for the Sims 3, but the release dates for any of these games can change at anytime.
Thank you for reading!