Hi there,
The Specialists will know best as they have all the scans and tests in hand and the knowledge needed to make a decision as drastic as Bypass Surgery. I am sure they are monitoring his condition and it depends on his overall heart function. Bypass surgery, or any open heart surgery, is very risky and drastic intervention, so they only do that when it is absolutely life-threatening.
The heart is wonderful by creating Collaterals, but that will help with some blockages, for a number of years and then, no more and that is normally why sudden cardiac attacks begin. There is medication to prevent further damage to the existing blocked arteries and to dialate the arteries and Lipitor and a heart-healthy diet and moderate excersice will keep the rest of his arteries clean.
All the best,