It depends on your level of patience. All I can tell you is from my personal experience when Google Now had been out for months and I was drooling for a chance to get my hands on it but had to wait until the end of March to get a new phone because my old one which went on sale in March 2011, and saw updates from carriers instead of Google - wasn't being updated that far, ever. I vowed never to put myself into that situation again.
I hear what you're saying - that Google is moving towards a new update method by pulling the API's for all of its services out of the OS and into Google Play Services, which will allow people on older versions of Android to get improvements to the Android experience via app updates rather than OS updates. And I agree, it's a fantastic move... with limitations.
I can't help but see this new approach as nothing more than a pause/play move by Google to allow the OEM's a chance to catch their breath, and also to mitigate the criticisms of "fragmentation" often leveled against Android by others. Certain more heavy-duty innovations can't simply be pushed as app updates and will have to be placed on a major OS update. Even Google themselves have publicly stated that this new method is not to be taken as an indication that they don't intend to continue updating the OS itself with major innovations. My earlier statement is meant to say that I do not want to be placed in the same situation I was before. When the next "Google Now" type of major feature to the core OS comes out, I'm going to want it immediately, not 4-6 months later.
Only time will tell us whether Samsung, HTC, Moto, Sony, LG and others will improve the timeliness of their OS version updates as they get a little older. We're not going to be able to know that until this year's flagships are about 1 year old. Right now they're showing us their good behavior faces because the devices are brand new, but given that the OEM's are in the business of making money by selling you new products every year, not by putting big efforts into maintaining the last year's models, I can't see them changing their stripes.