Your words are lost on me, then.
This is why I added the qualifier of "reasonable and practical judgment", because of course, if we don't have that qualifier, I could merely say in response to this that the Nexus may be a few weeks away, or it may be 10 years away, and expect you to accept that as a good reason to buy an already released device now. But of course, that would be a trite response of no real value, as you now see.
I see no point in these words. Perhaps you have a different meaning of "shelf life", as to me, that means how long it's in the store for, so after I purchase the device that doesn't matter. However, if by this you mean something in the terms of performance, then to that I merely and easily say, that the difference in benchmarks between the Nexus and the first quad-core will be greater than the difference in benchmarks between any superior quad-core which comes out a few months later (Though history tells us that no smoking will occur in those few months), and that real world performance is irrelevant because the differences would be so small as to be unnoticeable, and also that the myth of Nexus performance "keeping up" is shenanigans imo.