If you are looking to make a purchase, I recommend purchasing the T4i, or in the alternative purchasing the T2i. You can save a great deal of money by opting for the T2i, but it does not have the tilt-screen feature. The T3i did not contain many updates at all, so you should likely pass that over unless you find a really good deal. T4i does have some great new features, like the phase detection image sensor, Although there are likely marked improvements, especially with the specific lenses that Canon created, this camera will likely not come close to the quality you can expect from Sony. But is clear that Cannon is giving it their best effort! You can see more information about T4i: T4i vs T3i
The touch screen is a notable new feature of the T4i. Other new features in the 4 include the Auto Focus feature which is much like the 60D, and the inclusion of built-in stero mics. So there truly are some real upgrades in this version. One thing that did not get upgraded is the image sensor, which is a 18MP sensor that you will find in most Canon products. It is passable, but definitely falls short of the quality provided by Sony image sensors.
If you are a Nikon fan, you should probably skip the D3200, as it uses the Sony image sensor with 24 megapixels. This configuration is simply no good, and as a result, photographs taken in low lighting will be of poorer quality. You’re likely better off waiting to see what Nikon has up their sleeve for the D5100 update.
So if you want to save money, t3i or t2i will be a good choice, if the new features on rebel t4i are important to you, choose rebel t4i, you will never disappointed with it.