When you discuss image quality, there is probably no perceptible difference between your camera and a new Canon DSLR. Unless you are looking to do giant sized prints, maybe. Pixel count has gone up but that won't always impact your image quality. The Canon processor has been upgraded since your camera and that would make some slight difference. On a purely objective level, I see the sensor as a CD sitting on a shelf. Without a processing device, what do you get from a CD sitting on a shelf? The processor is, IMO, mainly responsible for the technical merits of the system yet the system can be no better than the CD/sensor allows. Keep in mind, most of the image quality comes from the processor once we remove the human element of photography*. Even then, there's still a lot of software between you and a finished print. Then realize the consumer level camera you own and the camera you would likely buy is marketed to a very broad base of users. The sensor and processor have improved but have those improvements really brought better quality for your use is the question to ask.
I'd put my money into better lenses/filters and keep the T3 if those were my choices. The only real world drawback to that scheme is whether you wish to remain a Canon user for the next decade or so. Once you've invested in a reasonable supply of Canon lenses, it's more difficult to break away from Canon in the future. A few of the other manufacturers have been gaining ground on the old standards and offer some very interesting alternatives. I'm personally not impressed by numbers alone so I am not seeing several of these companies as anything other than johnny come lately's trying to grab the less informed buyer with on paper specs. If I had the money and the desire for a new camera, though, I might be looking at the Fuji X100T right now. Keep the Canon as your all 'round DSLR along with the fixed lens Fuji as a team. Where Canon, Nikon, Sony, etc, have gone to great lengths to make their consumer level cameras rather sterile and robotic, the Fuji, by all accounts, is a camera which gets the shooter involved again in the process of taking great photos. Certainly, just handling a Canon/Fuji, Nikon/Fuji, Sony/Fuji, etc makes an impression. You'd have to do the same for yourself to see whether I'm right or wrong on that.
A few features have been added to the Canon line up which can make the process of taking a photo more efficient. The SL1's touch LCD screen is, IMO, very helpful even if it is fixed rather than articulated. With a nice compact body and a single focal length prime lens (the new 24 mm and the 40 mm primes are nice quality for not gobs o'cash), the SL1 can make for a very "pocketable" camera you can take virtually anywhere. Image quality though is more dependent on your capabilities than on the SL1's technical improvements over your camera.
Little improvement in Canon entry level DSLR s over the years Canon Rebel EOS 1200D-300D Talk Forum Digital Photography Review
You can use the dp site's side by side comparison page to look at your camera vs any other on a strictly numbers based evaluation;
Side-by-side camera comparison Digital Photography Review
* "Add to that the little known fact that about 90% of our digital image is created by our processing software
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