Yes, Guitar Hero 5 is getting all modern-like and letting those who buy it -- and own other GH games -- access all those songs they already bought (on disc or in DLC form) without firing up another title. GH5 and the upcoming Band Hero will work with songs from the Guitar Hero World Tour and Guitar Hero Smash Hits game discs, along with GHWT DLC -- even on Wii.
PS3 and Xbox 360 owners who own GHWT will be able to download a free update from within GH5 that enables DLC backwards-compatibility (for 152 of 158 available tracks) and adds new GH5-specific features to their existing DLC. In order to rip the tracks from GHWT and SH discs will need to purchase what Activision says will be a "nominal re-licensing fee" and have the unique 20-digit code on the back of the games' manuals. As with Rock Band 2, all songs from the discs will be ripped to the systems' hard disks, but unwanted tracks can be individually deleted.
The process will be similar on Wii, with a couple noteworthy differences. First, DLC must be re-downloaded (to add new GH5 features, plus they'll sound better) either en mass or track-by-track to the Wii's internal memory or (thankfully) SD card. There'll also be an individual song copy option for importing disc-based songs from GHWT. Now to find out what those six DLC tracks that aren't supported are ...