The main spec lacking on the new MB is an LED backlit display. This would give a brighter screen with less weight, size, and power usage.
The main reason why you would hold off on the MBP is because it has been out so long without a refresh (excluding the 2.6ghz). Many people expect a radical design change.
On upcoming products, it's mostly predictable what Apple will use for internal core components (cpu, chipset, gpu, etc.) as there are only so many options out there, and all available to Apple's competitors.
For design however, Apple can really pull something out of their hat. However, being first onboard for any of their new stuff is rarely a good idea.
Just read these forums after any product launch!
That said, buying a mature product usually means it has been refined through many small improvements in the manufacturing process.