Yes there could be a drawback as in Masters degree, they teach concepts that are more advanced than that of Graduation level. So they expect the students to know the basics before.

You you may face problems with the course pace and a difficulty in understanding the concepts.

Also during the recruitment, there can be questions on your stream, that if you had done B Com then why did you come for journalism now. You may face a problem in being recruited due to this.

But the scenario is different for every individual. You should definitely pursue it if you are confident about you career decision. No one can stop you. All the Best!!