Mercy will be the most picked support hero for as long as she still has rez. Hence why they're never gonna solve the pickrate unless they get rid of rez which they'll never do
We'll see the beginning of a Moira-Zen dive comp, I'm willing to bet. Mercy will still see lots of play, but those two together can do some serious damage, plus their, "throw and go," healing lets them have a little more free rein over their damage output.
Even though i'm Mercy main i have to admit i think Moira will take her spot. At least this finally gives me a chance to take another hero as well! ^__^