Its difficult to judge; OpenSUSE by its very nature is untrackable, because there are no "subscribers" to count. SLEx is probably trending down, as Ubuntu is a more popular "commercial" package these days and Redhat has most of the remainder.
Linux is mostly seen in "back door" installations; Increasingly, appliances seem to be Linux or BSD based, and most datacenters have a few linux boxes beating away on repurposed hardware, with no real record (as there was no CapEx requirement) where senior management would see it. Often they can be found by what is *not* purchased - such as buying a instance of Oracle, and hardware to run it on, but no operating system to stand between it and the hardware.
Larger adoption (ignoring the most popular distro, just in general) would be a good thing though. There is a certain catch-22 in that big hardware vendors and software vendors happily jump though M$'s hoops to get their products approved for that platform, but Linux often gets at best a late and non-optimized driver/version, and at worst threats of lawsuits against anyone brave enough to attempt to reverse-engineer the closed source driver to write a Linux workalike. Vendors uniformly blame this on the lack of adoption of the platform, and correspondingly, those who don't adopt the platform blame the lack of vendor support.