I am currently working on a side-scroll 2D game using unity 4.6.3 , about half the way there
Should i move my project to unity 5 or keep use the current version?
If it’s working fine for you, there’s no reason to move.
The later in the project, the more chance that you will have problems moving to Unity 5.
So if you think there might be something in the coming versions that you’d want to use, might as well do it now rather than wait.
Also, if you’re using Unity Free, then Unity 5 has most of the previously pro-only functionality in the free version. As far as I know, the latest unity 4.6 does not include all that. One good example of something that is now free and might come in handy is the profiler which you can use to debug performance issues.
I am in the same situation using Unity 4.6.0f2 for my current game project. Like @hippocoder said if everything is working fine for your project in Unity 4.6x there is no reason to move now. You would probably need to do extra work updating code for changes in U5 based on posts I have read.
I don’t see anything in U5 as a reason to move other than the Profiler would be very nice to have. Currently I just use my own profiling code to find bottlenecks in my code and keep an eye on what the Stats panel is showing for draw calls and vram. With my projects I can’t see ever bumping into graphics performance walls. I’m not big on the whole graphics thing, actually could care less about how awesome a game looks as long as it is fun that is what is important to me. But if you place a lot of value on “raw” graphics quality that may be a good reason to consider upgrading now.