Yes and No...
Any model which has access to the armory may buy Jump packs, but not all members of your Command Squad will have access to the armoury.
Now its possible to get upto 4 total models in a Command Squad access to the armory (Vet Sgt, Company Champion, Standard Bearer, and Apothacary).. that would leave you with 1 marine (in minumum squad size) without a jump pack. Now once that lone marine is dead your Command Squad would be free and clear to jump around so to speak. Of course that only gives you your character(s) and 4 guys with jump packs.. not as great as the assualt squad minus your character having furious charge. Not to mention more expensive as you have to give each of the specialists Terminator Honors to get access to the armory. Thats a minimum of 75pts a squad member... very expensive.