I think Flash Sentry on Season 4 wont ruin the show.Its cute the way they ship Flash and Twilight toghether,not putting much attention on "romantic" details or actions.I think a ship between the 2 of them would be okay if they dont make a big deal out of it.They should develop their romance or whatever you want to call it,slowly,starting from just a crush,to a bigger deal althought they should stop developing the romance when the reach the boyfriend stage,so girls wont lose interest.This wont ruin the show,but,if they make a huge deal,smaller girls(wich are their priority audience,girls from 5-11 years old) who arent interested on romance or boys will lose interest on the show and only bronies will whatch it,not including,those who dont accept this ship,and those who dont whatch the show.But still i think it should remain(for now) as a simple crush,althought,other sites have confirmed that someone who works in the show,apparently a producer,confirmed that NOTHING related to the Equestria Girls movie will afect or appear in Season 4 (like most show with a movie,the movie wont have to deal with the show),but still that,for me,is unceratain because i havent seen any tweet (the supposed source of the producer) that clears this thought,as soon as its confirmed,it will be clear if Flash will appear or not on the show.It also looks like Flash isint that interest on Twilight,as much as she is interested on him.(PS.Sorry for the long post,just giving my opinion also the pic included its part of the movie)