Only three (well 2.5), a 930, the 928 and a 550 which is the 0.5 because it's a replica, not the $500,000+ real deal. Since early Porsches were just fancy bodied VW's it's quite a faithful replica for minimal money, and probably the cheapest way into a mint 50's classic.
Porsche are going to do another 928 for compete against Scaglietti etc. The four door 928 'Panamera' has been a known project for some time, a two door version is rather inevidable. The Panamera will be awd with Cayenne derived V8 and an optional hybrid system. Cayenne also goes hybrid for '08. 911 may get jacked up and turned into a small off road coupe.
I doubt the new 928 will look anywhere near as good as the original, and the chassis is still well up to today's standards, as anyone will tell you, it's fully adjustable suspension made it the best GT until the Ferrari 550 (ask Wheels magazine etc). All it really needs is a new interior (fantastic for the 70's, less so today), and more power. In top spec they only had 350hp which is just not enough today. If my engine ever breaks (they have been known to go for a million K's), I'll put a Toyota (yeah I know) turbo v12 in it