Glyfair-
The following is mostly speculation, but I do have some familiarity with patent law. Note that I am operating on the assumption that, while wotc may have only most recently mailed wizkids about the patent on the 21st, wizkids has probably been aware of the impending patent grant for years.
Wotc started the patent process for CSGs some time ago. I don't know if they have a strong patent claim or not, but apparently it was strong enough to get through the patent office- which isn't the cakewalk everybody on the internet says it is.
Somewhere along the line, other companies started publishing CSGs. Wizkids has one of the more popular ones, with their Pirates game.
Wotc couldn't do a damn thing about this until they got their patent granted. But they sent some letters to wizkids saying, in essence, "Hey, we see what you're doing over there! You've got to pay us for the rights to that!"
Wizkids said, "Up yours, you don't have a patent yet."
Wotc said, "Fine. But just you enjoy the success of your product, because the more heavily you invest in it, the worse off you'll be once we own the patent on CSGs."
Wizkids said, "Crap."
Time passes. Wotc gets its patent. They don't have any intention of suing Wizkids per se, because they believe that Wizkids will negotiate a license with them. They make a public statement to the effect of "We don't intend to sue wizkids, erm, did I say wizkids? I mean, other industry players. Not wizkids specifically of course. We dont' intend to sue other industry players, right now."
In a stage whisper they say, "Did you hear that wizkids? The important words were RIGHT NOW. We don't intend to sue you RIGHT NOW. Because you're going to be reasonable, aren't you. Now about that licensing agreement?"
Wizkids decides that they'd rather fight this in court than negotiate a licensing fee. Or, they decide that they feel they can better negotiate a favorable licensing fee if they put some pressure on Wotc by filing a lawsuit in a court of their choosing.
Patent law allows someone who fears that their business practices are of questionable legality to file a lawsuit to get a court to decide once and for all if this is the case. This is so that businesses don't have to operate while every day wondering if today is going to be the day that they get sued for patent infringement.
So wizkids takes advantage of this and files.
And hear we are.
So what happens next? Probably the case drags on a while until wizkids and wotc come to a licensing agreement. If wotc's patent is strong, wizkids will pay through the nose to avoid havng a profitable product shut down. If wotcs patent is weak, wizkids will make a token payment and the case will settle.