try "apt-get dist-upgrade" and you will get additional information. some thin like x additional packages will be installed and y packages will be removed.
After you will get this information you will get question continue you can answer NO. But you will get answer.

Package is not upgraded by "apt-get upgrade" if is necessary to add new package or remove some package.

You can put result of "apt-get dist-upgrade" here and somebody will tell can you do it or not.....