I have not seen the vouchers, but I have heard that they do not carry an expiration date. With regard to your second question, and keeping in mind that I am not a lawyer, I believe the conditions of GPLv3 only are applicable to code distributed under that license. It is not clear whether the Linux kernel, which is currently under GPLv2, will soon (or ever) be licensed under GPLv3. Therefore, I'm not sure the release of GPLv3 will affect this issue of Microsoft's claim about intellectual property and its patents.
Please keep in mind that Microsoft has not threatened lawsuits; they state they are interested in being paid license fees for access to intellectual property for which they hold patents.
This was first published in May 2007