Porsche are not interested in joining F1 under the current regulations. They want F1 to change to suit them. Surely, also, they will not be interested in joining F1 unless they believe they have a very very good chance of winning championships in a very short space of time.
On the other hand, F1 is not going to change to suit them. F1 will change to suit their existing teams and manufacturers. If that fits with what Porsche want, then there's a chance. But think about it. If the existing players think that any proposed changes will suit Porsche and that they could enter and beat them, are they really going to vote in such changes?
I hope F1/Fia learned their lessons and do not try to please any specific manufacturer(s) inside or outside the current grid anymore. Set the rules wisely(!) and be done with it. If manufacturers want to play along, they're welcome to join -- otherwise, just skrew'em. Do not give them (too much) influence on the technical framework.
