The Creative Suite release cycle is usually every 18-24 months. As CS5 was released in April 2010, it's likely CS6 will be released sometime between October 2011 and April 2012.
I'd upgrade now if I were you! :-)
but heard that CS6 is on its way very soon.
And JFK said that there would be a permanent US base on the moon by 1970... Buy it, if you think you need it, the rest is just the rumour mill making overtime... Everything else is really beside the point.
If you are geared up for 64 bit and have lots of Ram then CS5 is definitely worth it.
I say, "Wait for CS7."
Historically, the time span between CS upgrades is roughly 18 months. CS5 was released in April of 2010, so I wouldn't expect CS6 until late fall/early winter of 2011. Now Adobe could release CS6 next week or 2013, so it's anyone guess.
However, the big holdup for CS5 was moving so much of the Mac code to 64-bit. (I believe the only remaining major 32-bit Mac apps are Illustrator, Flash, InDesign, and Encore, which may never *need* to be re-written for 64-bit).
So if you can recoup your CS5 upgrade costs in the next 10 months, I would do it.