I've jumped between various virtual machines over the years -- Virtual PC was my go-to choice until Microsoft stopped supporting it and my needs grew beyond Windows emulation. These days VirtualBox and VMWare Player do the job, but a lack of major updates to the former could see the Oracle-owned VM left on the sidelines.
Phoronix's Michael Larabel has questioned Oracle's commitment to VirtualBox, with the software seemingly in "maintenance mode" since the release of 4.3 in late 2013. Larabel goes on to mention that even with the stagnated development, VirtualBox is still the superior choice for 3D-accelerated Linux guests.
I can attest to the easy setup of VirtualBox and despite having some issues getting the virtual additions working in some guests and laggy mouse input, I'm more than happy to stick with it. That said, no one wants to go to the trouble of setting up a virtual operating system on a VM that's unlikely to see serious updates.
Larabel alleges that VirtualBox has a mere four developers on its team, citing a "reliable Oracle customer" as his source. If this is indeed true, it says a lot about Oracle's opinion of the VM's future.
Fortunately, there are a bunch of replacements available, from the fast-improving to the stable and mature, including KVM, Xen, Parallels and VMWare's assorted offerings, so it's not like the situation is dire.
Does VirtualBox VM Have Much A Future Left? [Phoronix]