The likelihood of finding a user who owns the
exact same specialty product of interest,
and uses the exact same specialty operating system,
and is relevantly knowledgeable in your question,
and is looking when you ask the question, is related to the
Drake Equation. You're probably not the only Solaris Canon plotter user, but proving this may be difficult.
You obviously know wa more than average on the subject already if you understand there's standard languages a printers can communicate in. We're not ignoring your question, our experience isn't specialized enough to answer. I'll give you the best guesses I can.
Dropping support for a portable printing language in support of a new and proprietary one would be an atrociously bad sign. I would not buy a hyperexpensive specialty product until I could prove it worked.
Perhaps Canon would have something to say on the matter. Maybe they will offer HP-GL/2 as an option, understand how to configure it, or suggest an alternative product which still has it.