You can often find refurbished units for sale by Apple which are covered by the same warranty as a new unit and have been fully tested by the Apple techs.
Are you using it for business? Apple has a leasing option which may suit your needs until the new version comes out. I share your concern as well about the future of the Mac Pro but the good news is that there is no news. Apple usually doesn't wait this long to announce and end of life to one of it's products. It's very possible that they were waiting for the right parts and possibly the release of Mountail Lion. True, Suitabe processors came out quite a few weeks ago but I think a suitble thunderbolt option was just made available for the Mac Pro..
I would say if there's no word about the Mac Pro by the time Mountain Lion is realesed it may be worth considering other options in the future.
I do pro graphics work in the Action Sports industry on a 2007 mac pro 8-Core and it's still going strong.. sure I would like it to be faster but it's still not too bad!