Honestly I doubt if there will ever be another Zep. I think the music scene would need to revert back to rock as the dominant force before it happens. Zep was great because they combined aspects of everything relevant in the late 60s rock scene into a modern (at the time) package - pyschedelic, hard rock, blues rock, folk rock, and even a little bit of southern/country.
Anyways give these guys a listen and see what you think.
The Parlor Mob (closest I've heard to a Zep epic is on Tide of Tears)
A bit harder to track down but seek out these albums for some Zep inspired rock:
Leafhound - Growers of Mushroom (raw early Zep sound)
Ozz - No Prisoners (imagine if Zep made it to the 80s and wanted to be more mainstream)