Yes, the "es" was intentional. We all know that the next Expansion is going to be Hobbit Saga and with it comes 5 heroes (1 for each sphere + Bilbo). Currently we have 7 Tactics heroes and 6 heroes in Spirit, Leadership and Lore. I for one would not be surprised to see FFG replace 1 set of player cards with 3 heroes. Meaning that Shadow and Flame AP would contain heroes for Leadership, Lore and Spirit. Giving us a total of 7 heroes for each sphere.
FFG has thrown plenty of curve balls throughout this cycle when it came to the heroes they released ie. a 2nd copy of Aragorn and Glorfindel, putting out a 2nd tactics hero before giving us a spirit hero. (Plus for those of you that play AGoT LCG we just recieved 3 plot cards in the same pack instead just the normal one.) Nothing is set in stone to say the least.
Now this is all speculation and I won't count on seeing 3 heroes in SaF but I just have this feeling FFG has one more curve ball to send our way in the Dwarrowdelf cycle. As for the hero (or heroes) that will show up, who knows? I thought it was going to be Glorfindel in the last AP and surpise surpise he skipped head to FoS.