One of the mods they use I believe back gens ores gen for new mods. I don't know the name so you shouldn't have to restart later barring some massive game glitch.How about a real question. What mods are the devs looking at to add later once those mods become stable? I'm sure you're looking at Thaumcraft. Are there any others?
And, given that, if the mod you add later gens ore, does that mean we'll have to move to unloaded chunks once the mod is added?