What others Superstars DC can put on Action Comics right now? I can see Ram V making a short arc, Tom King, Cantwell work in B&B was in continuity and left the door open for more, Kelly Thompson is a good option.
From Marvel names I would like to see DC get are Hickman, Kieron Gillen and Jed McKay, but I'm pretty sure McKay is exclusive. Gerry Duggan just announced he is leaving the x-office soon, and he made some work for DC recently. Ewing, is also exclusive and is clearly one of the creators Marvel is making their main guys so I doubt he will be working for DC in the near future.
From outside the big 2, I could see DC going for Scott Snyder, Rucka would probably come back for a Lois centric arc, Fraction could do some good stuff. Mark Millar have been teasing Superman in his future, but he probably will do some Black Label or Elseworlds.
And we can always dream about Gaiman, Morrison, etc.