Just remember, the modern Fender will be old one day too. So just go on ahead and save yourself a few thousand dollars.
It's not
just a question of age though, is it

? "Vintage" is not a word intended to reflect only the age of something, but rather to indicate that something came from a special period of high quality/desirability

.
Modern 'standard' series Fenders use different materials and construction techniques, as well as different hardware, to the older basses. As a result, they sound and feel different. Some players feel that difference and decide that they prefer the older models - some don't. This partly explains why re-issue models are so popular - people don't want them because they
are old (they're not), they want them because of the different tone and feel (and possibly, the look). The point is, there are a large number of Fender fans out there who regard "the vintage years" to be around the late '50s to mid '60s.
Will a 2005 (for the sake of argument) American Series P Bass be exciting the masses in the year 2055? I somehow doubt it, but I could be wrong

. Apart from anything else, there are far more of them made now than in the early days of Fender and they will last a lot better than the nitro-covered '60s basses, too, making them far less rare.
Besides, there are many more playable, excellent and exciting basses from today for a 'vintage' collector of the future to choose from

. When Fender were making their (classic) pre-CBS basses, there wasn't much else around to get excited about (Rics, maybe

).
My point is; vintage Fenders ('50s/'60s) today are seen as 'something special' - when today's Fenders become old, they will probably just be seen as ... old

.
Just my $0.02