Shimano 105 10 and 11 speed compatibility Currently I have on my bike the Shimano 105 system (2 years old) with 10 speed cassette. Currently I am buying a new wheelset (Fulcrum Racing zero) made for Shimano 11 cassette. I was told that I can use my 10 speed cassette but I was planing to upgrade to 11 speed cassette in the future. Is the Shimano 11 speed cassette that comes with the latest Shimano 105 compatible with older 105 systems?

I apologize in advance if I don't make myself too clear.

Thanks for any help
If you want to go from Shimano 10 speed road to 11 speed road, you'll need a new cassette, new shifters, a new chain and a new rear derailleur, since the cable pull ratios have changed (again). Zinn also notes that 10 speed FD might not shift as nicely as 10 speed FD with the 11 speed shifters, so may as well throw one of those in. 

So, in the drive train, essentially all you'd be wanting to keep is the crank if you want to go from Shimano 10 speed road to Shimano 11 speed road.