Japanese-language site Macotakara says a new 15-inch model has entered the test phase. It's not clear at this point whether this will be an addition to the MacBook Air series--currently offered in 11- and 13-inch sizes--or a new MacBook Pro. One tech site claimed back in July that a 15-inch model would be part of the MacBook Pro line. Macrumors, which also supports the MacBook Pro theory, had originally reported about an ultrathin MacBook back in July. Presumably, a Mac laptop as thin as the Air will not have an optical drive. That would be in line with the handful of ...