IMHO, the Linux monoculture prevents sometimes from adressing specific problem areas (at least it slows down things enough to miss the target).
Linux is not yet totally ubiquitous - the most recent example is the Android "port" (which involved a lot of domain specific hacks). It will probably never be because it's probably impossible - nothing wrong per se by the way, it has already gone a long way towards the general usefulness goal.
But some areas may benefit from the immediate availability of an alternate (possibly less versatile) free software solution: security box, wifi boxes, GSM phones (look at the "OS" selected for OsmocomBB), home automation devices, networking equipment; possibly: supercomputers, industrial control systems, industrial embedded systems, etc. 
Personal computing devices are not the only computers in modern information technology, they may not even be the most important ones - even if they are surely the most *numerous*. (What would you miss more: your smartphone, or your bank central computer?)
IMO, the BSDs should be seen as an opportunity to adress some of those specific concerns that necessitates a full OS too . BSDs developpers seemed to agree as they initially selected some specific target (security, x86 perf., portability, distributed systems). However, up to now, maybe those projects primarily did that by themselves for differenciation or branding purposes  while they should be given true opportunities to aim an important target.
And specifically, Linux should *stop* claiming these targets (because they are for the BSDs).
Sounds like political movements are needed: bringing up an alliance between all the "freedom" partners should be on the table, with the objective of settling on a long lasting treaty. It seems to me that this is necessary to refuel some allies again, up to the task.
 IIRC, sometime in the 90s, the Fermi lab linear accelerator needed an OS for a VAX. Only a BSD fitted there seriously. That's a single computer in production, but well... only two such scientific equipements have ever been built in human history (Fermi Lab and CERN) so... point gained.
At some point in time, it seemed like OpenBSD was targetting the specific area of an intra-network OS (highly secure, IP/TCP but also BGP, OSPF, NTP, etc.), but I suppose Linux claimed that target too.
 Possibly not DragonflyBSD ;-)
 I mean, do you really trust Cisco or Huawei to transport your packets on wire? Or Apple and Google your packets in air? Whatabout transporting yourself?
 But not as full as Linux...