I am not sure if this is the same play that I linked a while back, but something is planned for the 22-23rd up in Edmonton, Alberta in Canada during the CapitalEX event.
It sounds like only three of the mane six will take part in the show. Have a copy pasted excerpt from the site!
My Little Pony…stars Twilight Sparkle, Rainbow Dash & Applejack in a live, interactive, musical adventure. Twilight Sparkle is a light violet unicorn pony with an indigo mane and tail and pink and purple streaks, in the pursuit of knowledge. Applejack is an orange earth pony, with a blonde mane and tail, very dependable and down-to-earth, but also has a stubborn side. Rainbow Dash, a sky blue pegasus pony, with a multicolored mane and tail, very brave and bold, but also mischievous and proud.You can find the mane page here!
Thanks to Alberta Brony for the info!