The only thing to keep in mind is that if you have enabled 8.5 to prompt to auto-install the plugin if it's not installed, it will prompt 9.0 users to install the 8.5 plugin because it does not recognize this future version. However, if you cancel out of the installation it will still work fine. So I would recommend disabling the auto-install prompt in 8.5.
Well, I have never heard of v9.00.7000. The first release of 9.0 was 7119. So I'm not sure what this version is, but it should probably still be backwards compatible with 8.5. However, I would highly recommend upgrading to SR4 (release 7469) because several key bugs specifically relating to IE Plugin backwards-compatibility were resolved.
Our users install the plugin from the link on the Access Point. Do you think I can just overwrite the existing plug in setup files on the server and when they click the "download plugin" link it will install the newer version?
I am now thinking that perhaps I should just Upgrade the whole server to 9.4, but I've got such a limited amount of time before we go live, I'm not sure it's a good idea.
Have you done the 9.4 upgrade? Is it very difficult?
It's not difficult to upgrade to SR4, but I would recommend you try it on a DEV box before you do it on the PROD box. That's just good policy. And, yes, if you download it from the AP link it should overwrite it too. You can stay on your current version of Server, just replace the executable C:\Program Files\QlikView\Server\QvClients\QvPlugin\QvPluginSetup.exe with the SR4 version. I personally don't like the link on top so I've written a little script that will automatically prompt a user to install the latest version. See this page: http://naturalsynergies.com/content.php?page=28. You would just need to replace "var _ = new ActiveXObject("QlikTech.QlikOcxCtrl");" with "var _ = new ActiveXObject("QlikTech.QlikOcxCtrl.9");"