If the aircraft is safe enough to fly as is, then it is safe enough to fly.
No, time and technology move on. Fixes do not have to be instant as there is a temporal element in ALARP. 'Temporal' cannot be used to stick your head in the sand or to avoid spending money either.
Collisions happen, regardless of equipment fitted and procedures followed.
No, with good procedures, training and the sympathetic use of technology the rate of collisions reduces significantly.