I'm going to be honest with you guys and say that I've never played a Dragon Quest game. I'm not familiar with the series but that doesn't mean that I'm not interested to know more.
The game is going to be released on the Wii and Wii U with the Wii U version having vastly superior graphics. The game will be able to be played online simultaneously with Wii owners and Wii U owners, so if your friend doesn't have the Wii U they can still play on their old Wii with you.
It will probably follow the same suit with Monster Hunter Tri in Japan with the game being a pay to play affair while the US/Europe version will be free to play (hopefully). Dragon Quest isn't nearly as popular in the United States or Europe so I can't imagine making us pay to play online being a very smart choice. Word has it that you can play with A.I. controller characters but after a few hours of gameplay you must connect online. You can play the entire game by yourself with A.I. characters but you will still be required to be connected online in a very similar fashion to Battle Net with StarCraft II.
The Wii version is gong to be released in 2012, while the Wii U version is TBA but I'm pretty sure that Square Enix will try their best to release both games nearly at the same time and close to the launch of Wii U. I'm excited to hear more!