Both make valid points, but I tend to lean toward not waiting since we're talking about a laptop and not an enthusiast desktop. For a desktop, they seem very interesting for the typical performance increase but also opening up overclocking again. For a laptop and the initial June release, I don't see enough power savings which would aid battery life, and the HD4600 shouldn't be that much better than the current IB HD4000. Maybe in Q3 the HD5000 will be well reviewed and give us better insight as to whether it's actually better or not, but to me it'd still only be a hint as to what Broadwell will be bringing.
If I were looking into a 17" laptop, I'd be just fine purchasing a current IB based model. But like nsafreak notes, waiting never hurts if your bargain shopping. It opens up your options and can usually fall back on Ivybridge at a lower rate if those are still options.
Forgetting microprocessors for a while, Windows8 might mature more in the laptop market by Q2/Q3 2013 as well and just be another viable option. It's currently not IMO as it just hasn't been implemented well thus far. I just saw an Asus with a touch-screen on the back of the lid, but the user side was not. Close, but no cigar! If both sides were touch, I'd be all over that thing. Here, Leo has the same opinion on the X202E VivoBook
(Start at 38:48). It's just something to think about besides the bits and pieces inside. Hopefully Win7 is still an option to fall back on too if we're still in this weird OS state of confusion.