My personal guess (and probably more than a few others) is that Sun is interested in taking the clustering functionality that underlies Lustre and integrating it with ZFS for a future version of Solaris. Even if Sun stops supporting Lustre development on Linux, its GPL open source, undoubtedly someone else will pick up the slack...
That could be. I have spoken with some of the lead cluster fs people (now Sun) about it. For the next few revs at least it will continue as a Linux product. ZFS will be put underneath lustre rather than ext3.
-- Andrew