2010 renewal eligability?

Hello

     Currently have 3-key NISS 2010.       Renewal upcoming in November, 2010.

If i can purchase a ''one(1)-key' version of NISS 2010 on sale locally at a great price can i use 'just' this one-key version or will my currently installed 3-key 'reject' being dropped- down to one key ? 

          Guess what i'm asking is must one 'renew' with the 'same' product - a 3-key version?  I also have no use for the 3 key version but that's what was on sale when i bought my currently installed product.

                 thanks in advance !  Edythe