I think basically now is the time to look hard at lens lineups and how they are different. But I think you're essentially in this situation: After 2 years of amateur photo, buy a new body or a great lens?, but with more freedom since you don't have a large lens investment.
If you're really hating the ergonomics of your current camera, or tempted by something on the market (maybe a switch to a mirrorless system), switching brands is worth investigating. But on the whole, the Canon 550D is a fine camera, and you are probably best off sticking with it for a little longer and investing that money in nicer lenses, before upgrading the body.