Lots of problems with launching a new car into this segment, namely;
1. Miata. The Miata owns the inexpensive roadster market and there is a new model already on the way.
2. Audi TT. Porsche has to worry about cannibalizing TT sales.
3. Nissan Z. The Z has more power and performance. Yes, the Porsche name carries a premium but ...
4. Porsche 924. A lot of people will associate the 551 with the infamy of Porsche's last attempt to create an inexpensive entry-level car and stay away.
5. Branding. Does Porsche really want think of any Porsche as "entry level"? That is what BMW's are for.
Thus, Porsche would actually have to deliver a better car than the competition at the same price point and this simply isn't Porsche's forte - and especially not when they are focused on selling $80,000 trucks to soccer moms, $100,000 sedans to Chinese businessmen, and $120,000+ varients of the new 991.