Update: As Destructoid points out, EA's also register TheSims5.com, TheSims6.com and TheSims7.com. Guess there's no need to call the Hardy Boys.
Original: EA has registered TheSims4.com, suggesting its currently working on yet another title in the series. Bet you never saw that coming.
The Sims 3 was released on PC back in June. EA will release console versions for 360 and PS3 later this year.
EA registered the new website at the start of July.
This could of course just be EA protecting its products, but with the company promising to reveal several games at its showcase in Tokyo next month, don't bet against this being one of them.