When I had contacted Pixologic previously the response I received was that they would definitely consider porting to Linux as long as there is enough interest from consumers to warrant the port. Since ILM, Weta Digital and other studios have used ZBrush at one time or another on projects it won't be just the freelancer or hobby artist that influences this port. The poll should hopefully provide them with a better understanding of how much interest there really is as long as people take the time to voice their opinion.
As for the programming issue I'm sure with enough interest from consumers to warrant a Linux port of ZBrush can convince the company to hire additional programmers to complete developement on time. After all the software has already been a success on Windows and OSX. They may also be able to attract interest from other programmers in the Linux community that typically work on open source projects as long as they sign a NDA since ZBrush is closed source.