I'm the mayor of an all-deer town (2nd time), and I must tell you that if you get an all cat town, you might get bored fast and regret it.
Since you like the villagers you currently have, honestly you should keep them, unless you're like me.
I have an all deer town because I loved Erik, Beau, Diana, Bruce, Bam and Zell, and since they're all deers, I though why not?
I grew to love all of them, because I noticed I simply love the deer design. It's perfect.
Of course if you really feel like it, and have some spare money, you could buy an extra copy of animal crossing.
Otherwise you get your cat town, and if you regret it, you just have to tt for a bit to get your current villagers back.
Or, just think about it for a while more. It's a big thing, chooing out your beloved villagers.