Just thinking out loud, but what do people think of the likelihood that Canon will condense the current 50L and 50 f/1.4 into one L option with a f/1.4 aperture?
Why do you think that a new 50mm 1.4L IS would replace the "normal" 50mm 1.4? Did the 100 2.8L Makro replace the "normal" 100mm 2.8? The L-Version will be weathersealed, with IS, red line, 9 Blades, ETTL-II and sharp wide open.
There are a lot of coexisting focal lenghts with L or Non-L. A further example would be the Canon EF 70-300mm f/4-5,6L IS USM vs. the Canon EF 70-300mm f/4-5,6 IS USM.
There definitely are co-existing L and non-L lenses. But in this case, there are four co-existing 50mm lenses (though, obviously the 50mm f/2.5 is designed for a different purpose).
My thoughts were:
1.) In general, DSLR and lens sales are not growing like they have in the past and one way to increase profit is to lower costs, such as production costs. This could be done lowering the number of production lines over time.
2.) While a 50mm f/1.4 can definitely give you a depth of field that a 50 f/1.8 or f/2.0 IS can't (presuming that one is coming in the relatively near future similar to the new 35, 28, 24mm primes) given the price increase that we've seen on those lenses, it will be much closer to, though likely over, the price of the current 50mm f/1.4 than the nifty-fifty it would be replacing. Unless it's going to be in the $800 to $1000 range (which seems awfully high, especially given the price cuts they did on the non-L primes) it wouldn't have a lot of price differentiation from the 50mm f/1.4. And given (presumably) 4-stop IS and sharp-from-max-aperture image quality that we would likely see in a new non-L 50mm lens, I could see many people shrugging off the older 50mm f/1.4 anyway in favor of the newer lens.
I suppose the other possibility would be that they keep the nifty-fifty because of its sales, and swap out the current 50mm f/1.4 for a narrower, image stabilized version and only bump the price up a couple hundred dollars.
So, in summary, yes I agree that Canon offers identical focal length lenses of various levels, but we're talking about four 50mm primes in their lineup. Given the need to lower costs over time to realize greater profit, as well as the need to price-differentiate there products efficiently, I could see the 50mm f/1.4 disappearing in favor of a f/1.4 L, and a f/1.8 or 2.0 with IS, keeping the high-volume nifty-fifty in the lineup for longer. Of course, I could easily be wrong, just speculation.