1. are you planning to have Dropdown editors for the custom columns
No the dropdowns will not be supported by the custom columns. They will be part of the "Resources".
2. Can I have images to show the color/ status of the task which should be editable
This will be also possible with the Resources.
3. Can I and or User change the color of the gantt on every task based on the status/ based on other business rules
4. What are the gantt control features you are planning on for the next release.
With the upcoming version the only one feature that will be added is "Resources". Here is the Roadmap
Gantt's resources will be similar to the RadScheduler's Resources:
I hope that I managed to answer all your questions.