Asriel on 10 September 2009
I'd expect Halo:Reach to take place on Reach, possibly continuing the stories of the Spartans left on Reach as Mendicate Bias says.
Also, there is no single Covenant homeworld... The plan for the Spartans was for them to find the dwelling place the three major prophets and kidnap one of them, to try and force them to sign a cease fire with Earth. The Capital of the Covenent was High Charity, where the major Prophets dwelled, which is featured prominently in Halo 2 and appears again in Halo 3.
