This is completely theoretical but what are my chances of transferring from UIUC to UCSD?

I recently committed as an incoming freshman to UIUC (University of Illinois at Urbana-Champaign). I will be majoring in history and probably taking up a double major in psychology and a minor in Spanish. This is all theoretical because I’m very curious. If I were to keep up excellent grades-3.7 and above, how likely would it be for me to be accepted as a transfer student into UCSD for my junior year of college?
I plan to go to law school in California afterwards and the only reason I’m not doing my undergraduate in California is because I do not feel like I am ready to be that far away from my parents yet but I know in two years I will. I love San Diego and love UCSD as a school so that’s why I was wondering.