All,
After reading some recent interviews with David Ellefson, it seems like it was probably a good thing he isn't heading back to Megadeth anytime soon/ever. He has a lot going on--including producing/supporting a biopic about the late Nick Menza:

"One week until our campaign ends and we greatly appreciate all the donations. So far you've helped us raise a total of $7,629 to further our goal in completing our mission to bring you the official documentary film that will focus on the personal life and musical career of the late legendary Nick Menza who was best renowned as heavy metal’s fiercest drummer during Megadeth’s 10 year peak who died doing what he loved best!

If you haven't already donated to our campaign to help raise funds for the final production cost, there's a handful of lower level perks for $5 and $25 where you could get your name listed in the special thanks section of the film along with a special message that you write, limited edition merchandise, limited edition Megadeth tour laminates that were owned by Nick himself and signed by David Ellefson. Thank you everyone for the continued support in keeping Nick's legacy alive.

Sincerely, Menza Family"

The foregoing is from Ellefson's Facebook page