You're right, it's inevitable. For one thing, the old Class 5's are moving down below the "sweet spot" of price/performance. Dual/dual servers are giving way to dual/quads as quad-core chips become more highly available, and we're starting to see chips with more cores being sampled by Intel and AMD. All these, of course, are 64-bit capable chips, so it'll make sense to put a 64-bit OS on them. And that means the server software will have to be recompiled as 64-bit for optimum performance...which may take some time, if the code needs to be made "64-bit clean." I wouldn't be surprised if significant parts of one or more of LL's test grids (maybe not Aditi, but one of their internal ones) is now running 64-bit as they work out the kinks.

(Heck, my own office workstation is now an Intel dual/quad with 8 Gb RAM and a pair of 500Gb hard drives. Time marches on...)