I'm focussing on my Warmachine Khador at the moment, and will probably continue to do so for the foreseeable future. I don't see myself paying $50 for an army book for a game that I'm not playing a lot of right now.
That said, I am curious to hear what the new Lizardmen army book has done to my faction so that when the time is right (probably some time later this year when I need a break from stompy robots tzarist soldiers and decide to paint some stompy dinosaurs and lizard soldiers) I'm not totally surprised.
Also, assuming I had a fairly average 2k collection (except for having two Slaan for some reason that made sense at the time), what sort of stuff am I likely going to have to buy to continue to play at that points level? Do I need more of anything? Or is my collection still pretty valid and I'll just be buying the new terradons and sun-laser-prism-on-his-back-dinosaur-thing because they're awesome?