The general word on the street is that Porsche's Mission E can't immediately pose challenge to Tesla's Model S. All manufacturers will be playing catch up for years to come. On the other hand Porsche is a name that has built a solid reputation, not a secondary brand.
The question is, will Porsche built its own supercharging network or collaborate with Tesla? Porsche could possibly show some intelligence and collaborate with Tesla to take advantage of of Tesla's existing Supercharger network. Otherwise can they built their own?
Did you know Porsche Mission E Concept has a a hologram
A friend named Spectra Se, an a TorqueNews contributor writes "why is anyone building an electric car described as "taking on Tesla"? A Porsche is not a Tesla. It's a sharp handling sports car not a casual handling luxury sedan. Apples to oranges.
Another interesting opinion is that any car manufacturer that isn't actively working on switching its entire fleet to electric, non-fossil fueled cars, is spelling trouble for themselves. Porsche may be slightly ahead with the Mission E move than some companies with. The first company that truly mass produces an affordable electric car will be secure for decades, if not for the entire 21st century. Are Nissan and Chevy well secured for the entire century with with LEAF and Volt/Bolt?
On the other hand Tesla has a weakness. The company can't hit a production goal nor can it hit a price goal. The Model X was three years late and 10 thousand over what it was supposed to cost. A company like Porsche that knows how to build cars will come in a while up market share.