First, they said they can't promise you a permanent position because they don't want to box themselves in. They will compare you to the other seasonals that are being hired right now. You may be doing an amazing job but if there are a few new seasonals that do an even better job, you would be cut based on their performance.
Second, they probably don't want you to coast or ease up. If you know you are permanent, you might not try as hard. It is way easier to lay off a seasonal then fire a permanent.
Third, they probably don't want to open up the idea of seasonals being made permanent during November and December. If people found out you were made permanent, they would have every seasonal that wants to be permanent asking and inquiring about their status. It is easier just to make those decisions right after Christmas and inform everyone then.
Fourth, make your availability as open as you can without it affecting the important things in your life. For example, if you go to school, don't say you are available for any time that compromises your education.
If Target doesn't want to keep you, go find another company that will respect the job you do and appreciate your performance.