if there any plans to developing plugin for cpu scalling/cpudyn package to unraid 5?

cpufreq support is already there ... you have to load the appropriate driver.

Would it be some GUI to set the values for this 

Cpufreq is the plugin available for CPU scaling. You can download Xfce4 Cpufreq Plugin 0.0.1 if u want. It will show you the information regarding current CPU frequency and current used governor. It will also inform you about all available CPU frequencies, all available governors and used driver of the CPU. You will find that it’s pretty easy to use this plugin. All you have to do is select the CPU you want to monitor in the Xfce panel and change the timeout interval according to how often the information have to be updated.