I know you have more experience with the biz than I do, but going with my gut feeling, I think another U.S. tour with either NM headlining (I'd probably go) or with them supporting another good band (I'd definitely go) is all but guaranteed. The long gap between tours aligns with a long gap between albums. Right now I think they are ready for and working to make happen, a substantially bigger tour push behind Obsidian than they did for the previous two albums. I don't think their activity is going to decline nor do I think it actually has declined (in the past decade) despite their lack of headlining tours behind Enemies and Godless.
This is what I perceive: Nevermore's activity level has always been on the rise or trying to be on the rise, but after the last headliner (Dead Heart), their arc was eclipsed rapidly by other bands who were relative unknowns in the U.S. around 2000 but experienced huge popularity gains. In 2000, none of the bands including In Flames, Opeth, or Dimmu Borgir (for whom Nevermore later opened) had released their U.S.-breakthrough albums. Then there was a burst-year (2001-2003) where they released very popular, big-selling albums and they basically exploded "overnight", overshadowing Nevermore's steady, but slower, rise. So NM find themselves opening for the above bands. Even DEP on Gigantour 1 fits this criteria. NM probably understands this and for related or unrelated reasons decides to take a break; smart move on everybody's part. Now they're back with a long-awaited album for which anticipation has been very high and I bet they are ready to give a sustained touring cycle with maybe a short break for Warrel and Jim to do the Sanctuary album. I think in 2011 we will see more headliner tours and maybe tours in the support slot too but it will be direct support. I'm willing to wait and see.
