Canon may not be in any rush to introduce 14-24mm quickly in spite of all the hype in the rumor circuit...if it comes at all, it would be a pleasant surprise for those who are waiting....and not an expected obligatory move from Canon. In fact, some sober thought would suggest the wait is likely to be longer.
1) A minor issue is that there is no such thing as a "perfect" UWA zoom; the UWA designs are typically a jumble of compromises... and there *will be* no such perfection in the new Canon designs over and above the current UWA offerings. They may get it to be marginally better but they will face the same corner issues and will have to make compromises on distortion and vignetting and perhaps curved focal planes. So they won't be in a hurry to introduce yet another UWA zoom that comes up short…as it invariably will be given the high expectations.
2) Second problem is Canon's current line up on the WA and UWA end and its marketing strategy. The existence of a patent does not mean a product will be forthcoming soon. They introduced relatively in quick succession (not including the 17 TSE, and the 17-40L), the 16-35 II, and 14L II, and 24L II...and note all these are version II “updates”! A high quality 14-24 zoom that goes across all these will be an issue. Especially with the 17-40 and relatively young 16-35II already in the lineup.
So yeah... sorry to rain on the parade, but I am just not convinced that 14-24 zoom is coming anytime soon. If it does, I will genuinely be happy for ya.
While I agree that the 14-24 may take some time to materialize, your first and second argument are contradictory. As per your own argument the 14-24 will be a compromise of sorts so the IQ of the primes will be better. Prime shooters will still go for the primes regardless of the existence of the 14-24.
If this were the case, the 24-70 II would cannibalize the sales of the 24, 35 and 50 Ls. Don't see that happening.