What I have learned

When Canon upgrades one of their line of cameras the upgrades tend to be more evolutionary than revolutionary.  There are usually more storage in the jpeg or raw buffers and a few more auto focus points or a little faster shooting speed or start up speed.  Thus one should not upgrade from a T4i to a T5i to a T6i, the models will not be that different and will not be that much of an upgrade for the dollars spent.  The trick is to wait enough years for Canon to develop enough technology to add to their models to make it worth your while to put the dollars down.

Myself, I initially had a Canon Digital Rebel and upgraded after sixteen years to a T5i.  That was a big shocking difference between the two models, probably about eight generations difference.  I have compared the T5i and the T6i and found not that much difference.  I will most likely wait for the T9i or the T10i assuming that Canon lets the T series go that long.  Or I might move up to the enthusiast level of cameras and will skip over the 70d and 80d and wait to see what follows on from the 80d.

Any how I have learned that I need to sit on the bench for several years, much to Canon's chagrin.  Although my new old 5D2 was a big difference from the T5i and much harder to work with, but that's a good thing for me the harder it is the better makes me work harder and ultimately will produce better photography on my part.  I can practice photo composition with the T5i since its easier to work with and work on learning to work with the 5D2.

I wanted to write this on one of the Canon forums so that those that know more than I do can correct me if I have some misconceptions and perhaps some can add something new to their general fund of knowledge.