Congrats on finding a great car! I am sure that you'll never be happier (as I have been since I got my Boxster).
In regards to collectibility, it doesn't look good as Porsche has already made over 175,000 Boxsters and most of them have been very well cared for. For the foreseeable future (10-20yrs), low-milage Boxsters will be about a dime a dozen. Beyond that, its anyone guess but unless production numbers fall significantly, used Boxster prices will stay relatively low.
As long as you enjoy it, that is all that matters!
