It shouldn't be too difficult to localize the Wii version. In fact it makes a lot of sense to release the Wii version. Wasn't Namco using the amount of work and money that goes into voice work as an excuse for not having localized the majority of Tales games released this generation? If that's the case one would expect Namco to pretty much reuse the script for the Wii version in order to maximize profits. If the hardest and most expensive part of the process is already done, why not put a little extra effort into a release that will more than pay for itself?
Then again, the Japanese release of Tales of Graces for the Wii was a buggy mess, maybe they don't think it's worth the time and money to fix.