During these days, I found my usage pattern. I'll try my prime lenses first in most of the time. And I know that I don't mind to switch between lenses. When the prime lens does not fit the purpose, I will then switch to zoom lens.
I know one day I will be getting a few more prime lenses, and so I begin to look at the reviews and more importantly, the real star images from other people. I know that I will not go over 200mm and therefore, I will be looking at the standard to medium range first. For ultra-wide to wide field, I believe that going to full frame is probably the long term solution. Manufacturers are still pushing the number of pixels, but then to keep in APS-C size, there is not much room left before there is a big loss in image quality. And at the same time, the available options for ultra-wide to wide field is very limited, and maybe I can name the only one, i.e. the EF-S 10-22mm.
So, let's go back to standard to medium focal length, and there're some good candidates after some searching:-
1. Canon 85mm f1.8: this lens is inexpensive and the quality is still nice as I can see from others work, stopping it down to f/4 and it will work for astrophotography. The fast f1.8 is great for daily purpose.
2. Canon 100mm f2: this lens is simply superb! I would say it's a L lens without L (and also the price tag), but I guess with the superb Canon 100mm f2.8 macro, this lens is being over-shadowed. I believe that this lens is going to be very hard to find, even if I decided to get one.
3. Canon 135mm f2L: this one is again superb! Maybe with my mount, I should go for this one instead of my Canon 200mm f2.8L due to the shorter focal length and faster focal ratio. However, the 200mm can offer something with the Kenko 2x for me to the total solar eclipse trip and that's what this lens cannot provide. Therefore, I know that I ain't going to consider this lens in the future.
4. Canon 100mm f2.8 macro: this one is again superb! The macro performance is superb, and it can be used for daily purpose, and I even saw some great milkway shots with this lens! Maybe with the versatility, that's why the Canon 100mm f2 is so much neglected by the market entirely.
I don't know if you can smell that which one of the above will be my next target after reading all these. But I won't hide, it's most likely the last one in the above list.