It never hurts to wait, be sure to ***** your needs vs. wants. If your current laptop is doing everything you need it to, then there's no need to get a new machine, only a desire. If you can justify it based on that, and the money can't be better spent somewhere else, go nuts.
At the risk of going on a tangent here, I do know where you're coming from. I had an IBM tower several years back, one of the first Pentium 4's. That machine lasted me a good 6-7 years ( I can probably thank XP Pro for this, **** of an OS without any B.S. "bloatware") before I finally replaced it with an iMac in 2008. Although the last couple years were getting increasingly painful, I was always able to keep the thing running somewhat smooth. You'd be surprised what a difference a re-formatting / re-installation of Windows can make. I backed up what was important, and would start fresh with Windows and installing all my programs as I needed them probably about once or twice a year. It wasn't until about the last 2 years when I was starting to find it wasn't cutting it anymore. I of course had upgraded the RAM and HDD along the way.... Anyway I think you get my point. I had wanted to go Mac for a number of years, but in the end I was glad that I held out as long as I did. If I hadn't, I'd now have a G4 or G5 that is no longer supported as of Snow Leopard... Plus todays Mac's are cooler looking and less iRobot like =)
Just for the record, I have a 13" MBP i7 with none of the issues others are having with some of the new Sandy Bridge MBP's, though it's a good point that the next generation may have some of these flaws worked out or run cooler, IF Apple uses the next generation Ivy Bridge chips in the next refresh. Let's not forget how long they have kept the Core 2 Duo's going.