It has not been publically announced what will be the exact arrangement for WinWeb license holders at the time of .NETHTML5 release, but I have been assured there will be a free migration path for those who want to switch over to the .NETHTML5 version. Whether it means that you will get a new license code or if WinWeb and .NETHTML5 will share the same license code we do not know yet.
And yes, quoted directly from the License FAQ section "The perpetual license provides unlimited time development rights on the specific Major version of the license."
If you are still evaluating if Visual WebGui is the correct product for you, you can send an email to support (see my signature) when you are getting closer to the trial expiration and we will seek approval of extending that period. The worst case scenario would be a denial, where you would then have to purchase a WinWeb license, but I think it's worth the try.
Hope this explains,