Here's a question: would buying a FF camera mean you go out and shoot more with the new toy, improving your pictures because you're actually shooting more? Forcing you to go out and shoot because you want to justify the cash outlay?
Are there advantages to a FF camera? Sure. Better high ISO performance. Are there advantages to a crop-sensor camera? Sure. Lighter. Better reach.
"A few things like shooting at high ISO is not really a good thing with mine, color saturation is not as good, The image quality and sharpness in general"
High ISO noise can be cleaned up in post processing. Colour saturation can be adjusted in camera or in post. Image quality and sharpness? Shooting technique has a lot to answer for. Canon 550D? It's a 2 year old camera. It out-resolves the D700 I'm currently using. Image quality on DxO mark is not at the bottom of the scale and it certainly kicks the butt of my old Nikon D40x.
If you think of what you would spend on getting a FF camera and the lenses you think you need at the moment, you could travel to somewhere awesome and get some incredible pictures by being somewhere where crazy things are happening.
I hope you don't feel I'm telling you off. I'm just speaking from personal experience. I bought a D40X a few years back and went off on a long journey. While I was in India, a friend of mine took some pictures with my camera and they were so massively better than the ones I'd taken I had to stop and ask - what was he doing differently?
He pointed me at a book on composition when I got to the next big book store. I took a lot of pictures and began to learn by doing. I am still learning.
Question: What am I shooting with now? Nikon D700. Why did I upgrade? My D40X was stolen and so I had a clean slate to start from. It's cost me a lot to get FF lenses and insure the lot. Has it made my photographs any better? No.
Going out and shooting loads of pictures, looking at them critically, seeing what worked and what didn't work. Having people look at the pictures. Thinking of little projects like photographing friend's bands, going to festivals or taking part in challenges. Having to critically select pictures for a website gallery. Having to make a tight selection for clients who don't want to see hundreds of images. Those are the kinds of things that'll boost the quality of your images. Trust me. It is this that develops your eye and experience, not the camera you're using. Canon is one of the best camera/lens manufacturers in the world. It's good enough.
Hardware is useful. But it's just the tool. People were making prize-winning images before the 550D was made. People were making prize-winning images before the D40X and the D700. People are making great images on phone cameras. Get out and shoot plenty. Pick up a few books on composition. Go check out a few galleries like 1x or 500px and see what it is about the images you like. Trust me, that's the route to better images.
Mine is just one opinion among millions. If you do go ahead and upgrade your camera, keep a shooting journal and a periodically, look back on how you've progressed and see what you can attribute the improvements to.
Now go and find out and make up your own mind
Good luck