No, the new ones are having gps built in. It is not an option, it is the law. Here's a
link to nextel's gps enabled phones.
This article talks about one of the new phones, and
here is an article about sprint's gps enabled services.
Note the paragraph in that last article that says
"As required by the FCC, Sprint PCS plans to sell only GPS-enabled phones as of Dec. 31, 2002".
This pdf file from the fcc's web site documents their testing of built-in gps vs. triangulation for location determination.
This one talks about the timelines for the mobile phone companies to meet the 100% gps enabled guidelines. They refer to them as ALI capable (automatic location identification) phones.
ALL mobile phones are going to have gps, and while it is purportedly for your own protection, it does present us with a double-edged sword.