This hard fork is to do a change to the retarget algorithm. It is not a contentious hard fork. It is meant as a software upgrade and not to split off into two coins. If you are using a wallet, you must update your wallet. The old wallets won't recognize the new difficulty algorithm, so won't accept the new blocks as valid. Wallets that do not upgrade are likely to find themselves on a worthless chain. It probably will be a frozen chain, too, since I expect all of the pools and major miners will have updated their software.