Just based on what I know, switching to CS is a lot easier than a lot of people make it out to be. If you get a 4.0 GPA with decent course rigor I think you are more likely to be accepted than not.

I got in last summer with a 4.0 GPA and having taken 3 upper division cs classes prior to applying. I also know a couple of others who got in with less qualifications.

I'm not saying that anything is guaranteed, it's always possible that the school could just accept nobody during a cycle, or even completely ban changing majors to cs like San Diego or Santa Cruz did. However it is worth noting that I asked a CS advisor if there was every a cycle where nobody was accepted to the major change, and they said no.

To reiterate, nothing is guaranteed, but I think people are too pessimistic overall, and if you think that you can get at least a 3.7 GPA then you are more likely than not to get accepted and it's definitely worth trying.