So apparently Waid is in shaky talks with DC about working on some projects. Given that Millar is doing a Superman book, it's a pretty good bet to assume that Waid might be doing some Superman work if this news in true.
I could 100% see him working on issue #1000 of Action, but even before that I could see him working on a Superman book. Maybe co write Action with Jurgens? If it's not the 3rd coming of Morrison or Johns, Waid is the only writer that I can see them giving Action or partnering him Jurgens.
Thoughts? New? Speculation?