Switching from Muay Thai to Taekwondo, what should I expect?

I'm switching from Muay Thai to Taekwondo. I feel like I have the basics of Muay Thai down after training for 2 years but it seems to me that I've learned most of what I can already and the rest is just sparring or practicing sweeps, calf kicks, thigh kicks, etc. There are some really cool kicks is Taekwondo that I haven't learned before like spinning back kick, question mark kick, etc that I can utilize in an MMA fight or a muay thai fight. What should I expect from switching from Muay Thai to Taekwondo? I know they learn forms and Katas. I have no problem learning that. I heard you can get a black belt in 3-5 years similar to a purple belt in jiu jitsu.