How much will SOM impact the current TBC Classic player population?

I am just getting back into TBC Classic and have just started wondering about SOM and how it might impact TBC population.Will you be leaving TBC to play SOM? Do you see the population of TBC dropping drastically?I enjoyed vanilla/classic but would like to do arenas.Basically I am now confused on where I should put my attention/time because of course starting fresh with everyone sounds exciting.How are you all feeling?