New camera? Uncertain what to do?

I have a Canon Eos Kissx4, which is the japanese version of the Rebel t2i. I'm happy with its performance, having bought it for about $600 with a double lens kit about a year and a half ago. Now, my brother is looking for a used camera, and has offered to buy mine for $300 and I would upgrade to either a Nikon D 3200 or a higher-level Canon. Not sure if I want to yet. Thoughts?

How can we possibly give you an intelligent answer to this question when we know nothing about you.

We have no clue how much you have already learned, how much you still don't know, what purpose/genre you use your camera for and what purpose/genre you may need something better for. We don't know how much money you have, how much you can spare, and how much sense it makes for YOU to spend it when you're still happy with your camera, anyway.

Surely if YOU don't know the answers, a bunch of total strangers know it even less, right?

To me it makes no sense to switch systems. You're already familiar with Canon's quality and workmanship, you should have some lenses, why change systems? Sure sell the camera but me,
well I'm partial to Canon, stick with them.