Arduino Mega 2560 capability

Can An arduino mega be used to handle wifi, lcd display, video processing and an 4-axis bot. Just wanted to be assured that i am not burdening the 2560 controller a lot

Depending on the exact requirements (for example is is a 16x2 LCD or XVGA) I would say all of the above except video processing, no way it will do that even with nothing else to do.

Rob can suggest me something for video processing

A Raspberry Pi :)

Sorry I have no experience with video, but at present I don't think there are any Arduinos up to the job although it may depend on exactly what "processing" you need to do, how fast you need to do it and what resolution the video is.