As some of you may know, Thermal Expansion switched from Buildcraft Power, to something entirely different, that involves melting redstone. That kind of kills the entire point of New Tekkit: A single, unified, power source.
So what are the options?
The way I see it, there are three.
1. Keep it the exact same way. However, setups will be completely messed up, as MJ will no longer be used with thermal expansion. (From what I understand, a converter will be used for 1.6. But it may be removed in 1.7, or "The update the changed the world") In addition, it removes one of the key features of the tekkit pack: Unified power.
2. Replace Thermal Expansion with Industrial Craft 2/3. The new industrial craft is looking much better, and finally has some new features in it, after the relatively featureless 1.4 -1.5 ports. This also will disrupt setups, however, it will still keep a classic power generation, rather than a completely different setup.
3. Find another set of mods with a unified power system. This would mean removing Buildcraft however, which many players would hate.