American experience with the Phantom convinces the USAF that an internal gun is very necessary! If stealth is really that great, future air-combats might return to dog-fights between opposing fighters and a gun would then be even more inportant.
Where did you get the information that the J-20 will have 4 SR missiles? How would the 4 be configured? 2 on each swinged out hard-point? Is there enough space for 2 SR missiles?