I'm just as anxious as you probably are to get a working version of 3.9.
I can only assume they are not releasing it because it's not working to a level that would be satifactory for normal usage. I'd hate for 3.9 to be crashing, clicking/popping etc.....How far do you think they are away? Do you think it'll be weeks between the beta that must exist not to the release version? I don't know the answers to those questions. I'd love to hear an answer to those questions, and maybe James can offer us some answers. I doubt he will because, if he did and those dates weren't met there'd be hell to pay on this forum from a lot of users.
The problem is that they are damned if they do and damned if they don't. Release a public beta, and if it crashes and loses someone's project, or just plain doesn't work right people will be flooding UA with complaints.
People like you may (or even I) may want that BETA with the hope that for the most part it'll work. It sounds like you understand that the public beta may work or may work poorly in certain ways and you are willing to take that chance.
The thing is this; James from UA and other's have outlined work arounds for new G5 owners, that can't install Panther directly on their internal HD.
While this is a bit of a hassle, it sounds like a reasonable workaround and you'll just end up with an external drive they may not of wanted, but that drive will cost you about $120.
It also sounds like you and some others who are pro users are desperate to finish some projects. To me $120 is nothing to spend if you have multiple paying clients waiting on projects, not only is that $120 expenditure not too bad, but if I had deadlines and wanted to maintain a professional image that expenditure would be an absolute necessity and I'd consider it one of the costs of doing business. I have to say that I'm used to things like this happening and I consider it par for the course. If you are a pro studio/engineer and you are really feeling the hurt from a small expenditure then perhaps it's time to examine your career choice!
If you are a hobbiest, and budget is you main issue, then you'll unfortunately have to cool your heels and wait. You probably don't have deadlines and I'm sincerely sorry to say that the only thing to say is you will have to be patient.
Don't get me wrong I feel everyone's pain because it's mine as well. Tiger is great, I install Tiger as well as all my other music software on a HD I bought last week, just to get a jump on things before UA comes out with 3.9. So, yeah a BETA would be ok I guess, I'd prefer a working version that was solid.