Method one: concatenate into one numeric array, then split. This will not work of you do not have enough memory for the complete array. Where C is your cell array:
D = reshape(num2cell(cat(3,C{:}),1:2),1,[])
Method two: split into cell arrays, then concatenate. Does not require one large array to be sored in contiguous memory. Where C is your cell array:
D = cellfun(@(a)num2cell(a,1:2),C,'uni',0);
D = reshape(cat(3,D{:}),1,[]);
