|"Shrubberies are a source of|
many medicinal remedies."
Wait, no wavy red underline? "Destructed" is a real word? AWESOME!
*erhem* Anyway, this has resulted in people at my local FNM speculating that knights will be far less potent once Scars comes out due to the Knight Exemplar becoming less reliable.
I'm about to get into card spoilers beyond the existence of the "infect" ability, so if it bothers you that much, flee like I just said ni.
Thing is, however, the Knight Exemplar's boons aren't the only thing knights have going for them. For one thing, every knight in my deck has, or quickly level up to having, first strike. With the exception of a particularly nasty looking 4/4 dragon and a 1/5 horror, my knights are pretty well equipped to block and kill anything with infect without having to deal with -1/-1 counters. White Knights offer significant protection, and they're in my main deck for being 2/2 first strikers for WW alone. The protection from black is a happy bonus.
Plague Stinger, the flying 1/1 black creature with Infect, is a considerable threat given that it's flying, but my knights are still equipped to deal with them via my own flying creatures and creature removal spells. It's possible the flying knights in my deck will lose first strike should I trade my current ones for the weaker-but-less-expensive Kemba's Skyguard (2/2 flying for 1WW, gain 2 life when it enters the battlefield), but it still beats the Plague Stinger.
I'm not saying things aren't going to get more difficult for knights. The themes of Scars means much more -1/-1 shenanigans, be they via infect or something like Grasp of Darkness, a black spell for BB that gives a creature -4/-4 until end of turn, so the knights are definitely more vulnerable.
My point, however, is that I don't think knight decks will suddenly become non-viable. They will still be effective against other decks and capable of holding their own against infect decks. In fact, I look forward to facing off against an infect deck with my knights. Assuming I'm right, those will be intense, fun games.
Of course, that probably won't happen for a while if I get all the cards I need for my Myr deck before the first October FNM. Tap and roll out, Myrs!