Should I include my MSc admission in my CV?
I think it depends on where you are applying.  If you are applying to career-type positions, potential employers may be hesitant to hire someone they know will be leaving in a year, or less.  In that case, I would leave it off.

On the other hand, if you are looking for an internship, or a research assistant position, adding it may help build bridges between organizations.  For example, if you have the opportunity to work with someone who has a connection to the MSc program, this is a great way to start building a network.  This was the case when I worked in a lab between undergrad and grad school.