1. Is the new version drastically different from the version indicated above. Meaning, do they have to re-write a lot of code? - Drastically not, but there are a lot of changes like many new controls, skins, properties and rendering improvements that could require additional configuration and project changes.
2. Can the existing system work as it is (with minimal changes at the script level without touching code-behind) till such time their procurement process goes through? - It depends on the used controls and customization applied to them.
efore stating an upgrade of your project, you may find it useful to review the following resources: