+1I feel like we should start a petition to sigma:
... unfortunately, the less good/up to date/reasonably priced Canon lenses are around, the less reason there is to use Canon at all - for me, it's Magic Lantern, but if it wouldn't be for that I'd really think about switching to Nikon.
You are right. One of Canon's big strength is its high quality lenses. Nowadays the third parties are making really good lenses. Switching system is very possible. However, most people cannot make decision here are because they have many stuff for Canon system. That's why I also will stay with Canon for at least years.
By the way, Magic Lantern is very good for those xxD and xxxD. I used to love ML firmware for my T2i and 5D2. However, I think I don't need ML for my 5D3. Magic Lantern is not the reason to keep me staying with Canon already.