The successor to the current iPad is likely to be launched in the US on either the 2nd or the 9th of April, according to 'reliable' sources cited by a German website.
Macnotes (opens in new tab) writes that "the first or second Saturday in April will see the first sales of Apples new tablet. The iPad 2 will sell US-only for three months, and Apple Store-only for up to half a year. In July, more countries will follow. Walmart, Best Buy and Co. maybe have to wait until October until they are allowed to sell Apples new tablets."
Making the iPad 2 available outside of the US around July seems to make sense as it will give Apple time to build up enough stock to match worldwide demand.
It would be surprising for Apple to allow third party partners like Best Buy and Walmart to sell the tablets in October - a whole six months after general availability - simply because it would be unwise to alienate partners.
It's also unlikely that Apple will continue selling the current iPad alongside the iPad 2, which means that it will have to come up with something to fill the void or its partners will be all too happy to look elsewhere.
Macnotes says that the iPad 2 will feature "retina display", but have a lower pixel density than the iPhone 4, and come with a USB port and two cameras.