It appears as though wrestlers from Smackdown will be competing on Tuesday nights, while ECW grapplers will be coming to Friday nights every now and then, as well.
Here's the article stating as much from WWE.com:
WWE.com has learned that several meetings have taken place between Acting SmackDown General Manager Vickie Guerrero and ECW General Manager Armando Estrada that, if ratified, would allow SmackDown and ECW Superstars to compete on Tuesday and Friday nights.
While nothing is signed as of yet, locker room sources say that this open door agreement between Vickie and the cunning Cuban shyster will be discussed tonight, live on ECW on Sci Fi. No further details have been released, and when pressed for more information, Estrada was tight-lipped (a rarity in its own right).
"I have no news for you right now," said Estrada. "But tonight on ECW on Sci Fi (10/9 CT), I will give some insight into these meetings."