I have some good news for you. We are working on a refreshed look and feel for the Server and Data Center versions of Jira Software, Jira Service Desk, Confluence and Bitbucket (and for HipChat Data Center). This is based on the new Atlassian design and will include things like the updated colour palette, typography and icons.
A number of details will differ from the changes you've seen in Cloud products. For example, we're not currently working on large shifts to the navigation.
We want to give customers a smooth upgrade path, so we're specifically taking this approach for our Server and Data Center customers to make sure that add-ons and custom plugins continue to work and that customers aren't forced to retrain their users (e.g. for navigation).
At this point I can't give you any specific timeline for these updates, but I can share that it's something we are working on. If you have any specific questions, feel free to share and I'll do my best to answer.
Design Manager, Server
It's pretty lame if this is going to happen.
Don't understand why you tread the Server Software Users this way.
Especially because the Jira Cloud Instance has so many issues, especially on the Performance part. (At my Company we mostly suffer from slow instances to constant failures on the instance part.
Not my choice, I'm not Atlassian.
I'm not fond of the new UI, I think it needs quite a lot of work in usability terms. It's clearly less friendly than the old one in some ways. That said, it could work. I suspect part of the Atlassian approach is "don't clobber the server users until we've got it right"
It's always been time consuming. Apps for Cloud and Server use totally different frameworks. Whilst there's core logic and sometimes a bit of code you can share between them, on the most part, any app that is for both is two independent products.