You are right, this patch adds some hypervisor-specific code to the Linux kernel to make the detection of the TSC frequency more reliable and actually this is the only way to fix this problem. On the other hand, the code you mention is specific to VMware and emulating this functionality would mean to make VirtualBox appear a bit like VMware, ie. implement at least parts of the VMware backdoor. This can have negative consequences to other software which now could think that it runs straight on VMware and could use certain features of the backdoor which are not implemented.
I think we have to go this way sooner or later but this needs a lot of tests.