there is a minor difference in tooth profile between 9 and 11 speed chain rings... the cranks are the same... you can swap a set of 11 speed rings onto your present crank, and keep the octalink BB, if you wish.

the front der. will need to be an 11 speed specific unit for crisp, accurate shifts... same thing with the rear der., and some 8, 9, or 10 sp. rear ders. will have enough swing available, but the cages and rollers may not like the 11 sp. chain.

11 sp. specific cranksets are mostly a "hollowtech" variant... the spindle is incorporated into the right side crank/spider... there is also a minor realignment so that the chain line is corrected for the wider rear freehub/cassette... a mixed setup may find you experiencing extra noise, and possibly occasional false shifts when cross chained.

so... your present crankset will work if you install the 11 sp. rings... and will kinda work with the present rings... best situation will be an all 11sp. group, including the appropriate BB to match your 11sp. crankset.