There are rumours on the world wide web that Lukather has joined Alex Van Halen to complete a bunch of songs and recordings started before Ed's passing. Apparently Alex Van Halen has confirmed this to the Dutch newspaper De Telegraaf, whilst Lukather is reported to have commented affirmatively during Toto's recent tour of Europe.
In lieu of any official confirmation or news, I am not sure what to think although it would surely makes sense if they went down this avenue. @Andrew: Do you have any information to share?