Are you so sure of that? Canon has the EF and EF-S lenses, and not all EF-S lenses will fit on FF cameras because of the mirror striking rear lens elements. Nikon only has the F-mount in their DSLRs. I think you're mistaking Canon for Nikon.
Mind you, if you think that Canon lenses are the best because of the "L"... That's not true. Not all Canon L lenses are good (their 24-70 was especially bad compared to the competition). Most Nikkor lenses are good. Sony has excellent autofocus Carl Zeiss and also the G lenses. Pentax has excellent "Limited" lenses, etc etc...
Point is, if it's just because of the "L" label that you want to switch, you may gain nothing and lose a lot of $$$. You need to know exactly what you think is limiting you in your current system.
You really should list down the reasons you can think of to switch camps, and come back another day to look at the list objectively.
Question the points you raised. They may be based on misinformation.
In all likelihood you'll realize that there's little benefit to switching camps, at least from a financial standpoint.
Canon has a better lens range than Nikon? I've always wanted a 12-24 f2.8 from canon but unfortunately that doesn't exist. Both brands have their pros and cons for lenses. Can always go third party as well.