Yes, but many are claiming Mence has to be banned b/c it can only be revenge killed. If your not ready for Breloom when it comes out, you will still lose a Pokemon, but Breloom still isn't banned. Breloom also can't be revenge killed if it still has it's Sub (which it will, b/c the Pokemon out was asleep when KOd), simply Sporing the Revenge Killer as it breaks the Sub.
Um... lol. I'm sorry, but if you let Breloom Spore you and then don't switch out immediately you're begging to die. Why would you just sit there waiting for it to kill you? Unless Breloom was used in conjunction with a Mean Look BPer you're free to switch. If you don't leave the spored Poke in to die, Spore becomes worthless (assuming the spored poke has no Natural Cure) and any Ghost can walk all over the Subseeder and to an extent the Spore Puncher. So can any user of Taunt or Encore that can take a Punch on the switch. In order for Breloom to get a kill, the opponent has to A) be an idiot B) have the entirety of his team be either slower than Breloom or unable to knock it down to below 13% in one shot or weak to Focus Punch.
Put simply: Anything that doesn't get OHKOed by Focus Punch can walk all over Breloom, assuming you play correctly.
All you have to do is
switch out the instant you get Spored. Put in something that'll live through one Focus Punch and you win.
Relatively standard Brelooms can do one of many things on the switch: a) Sub b) Focus Punch c) Seed Bomb d) Leech Seed e) Superpower f) Swords Dance g) Facade h) Stone Edge or i) Mach Punch or j) Spore.
Intelligent players will Sub and then assess the kind of threat they're facing. These Brelooms can proceed to Leech Seed you and switch to a counter to what you put it after you break the Sub. This is less than ideal, but now Breloom is devoid of Spore.
Overeager players or those who are psychological warfaring you will hit you with Focus Punch. Meaning you have to be able to survive a Focus Punch if you want a guarantee of survival. However, if they do this, Breloom gets one kill max and then it gets revenged. Also, you can switch in a Ghost. Which is why intelligent players will Sub first.
Seed Bomb can't really do much to Breloom's most common switchins.
Confused players will try to Leech Seed before they Sub, leaving them wide open to be killed by whatever you switched in.
Anything that can take a Focus Punch can take both Superpower and Mach Punch.
Swords Dancing Breloom: Lol. As long as you can take an SDed Mach Punch and OHKO, or have priority that can OHKO, or a Ghost, you win.
Facade has 140 BP, which compared to Focus Punch's 150 + STAB isn't very appealing. Also it won't ever be SE.
Stone Edge means be careful. Salamence and Gyara are not good switchins. Honchkrow is a really bad switchin.
Spore does nothing unless whatever you had in had Natural Cure, in which case rinse and repeat.
If you don't let Breloom set up by leaving a sleeping Poke in, you won't lose more than one to it. Odds are you'll also be able to kill. Unlike Salamence, which doesn't need the opportunity to set up, Breloom requires the opponent to make a mistake in order to get more than one kill.