If they get a new younger bunch to take on the mantle from the old bunch, this is who I think could work
Obviously the characters don't have to be exact copies of the original film characters, nor do you have to have a black character to replace 'Zeddmore'. But I have sorta divided them into what type of person they would be, but that's just how I see them in their roles.
1. Luke Wilson: ladies man/charmer
2. Seth Rogen: tubby 'Ray Stantz-like' one
3. Michael Cera: soft spoken/wimpy/scared one
4. Ken Jeong: brainy/gadget one
I do think the cast would need to be smaller names rather than huge stars, but known stars of course. Off the wall type guys mixed with a sense of black humour and decent sarcasm.