The Tonight Show stuff getting ugly is just a sign of more to come.
NBC is doing all kinds of crazy talk. Guest hosts, for example, who will pretty much be any celeb they can con into crossing the picket lines. Balanced against some bogus claim that they, NBC, are only doing this to "spare the show's staff being fired".
Incidentally, Conan O'Brian and his staff are apparently getting the same kind of firing threats as Leno. And its of historical note that in 1988 (the sixth month long strike), both Johnny Carson and David Letterman (then both on NBC) folded and came back on the air, unscripted, under precisely this kind of "the staff will get fired otherwise" pressure. Except in that case, the network didn't apply that hammer until the strike had gone on for months, not days.
This is going to start to affect everything. Talk shows still airing, talk shows the networks want to get back on, reality shows, scripted shows where scripts are complete but they haven't shot them yet but where actors refuse to show up. Lawsuits and firings will be lofted around like missiles. And its not like the threats will all be coming from one side--the tactics are getting ugly on both sides. Ellen Degeneres has apparently already gotten ripped a new one by the WGA for going back on the air sans writers (because contractually her show has syndication contracts which can't be circumvented). The WGA says they are planning to specifically picket Ellen's show if she stays on the air. Degeneris' representation says that she's essentially in the same position as Oprah, Dr. Phil, Regis and Kelly, and other shows of that ilk, and none of them are being pressured off the air.
Here's an interesting tidbit: Courtney Cox apparently walked off the set of "Dirt", a show SHE produces. While a lot of producers have done that because they are hyphenates (writer-producers, I mean... think Tim Kring or Damon Lindelof), Cox is probably the first hyphenated-producer (in her case, actor-producer) to walk off their show strictly from sympathy, rather than being a WGA member.