In terms of Woods, I believe that there are some health issues that will never allow him to come back as he was. His play in the last 5 years has been pretty average (well below that for him but not of a great quality).
I believe he has used PED's over the years, we all know that he has used the blood therapy techniques which might be technically legal but are on the line for sure. Whether that is true or not doesn't really matter in my opinion. What matters is that for an athlete who is 38 today, he is much older than was Jack Nicklaus when he won the Masters at age 46 in terms of his body. Tiger has been playing competitive golf since he was 12 (at least), he reminds me a little of Kobe Bryant, he seems young since he skipped college but the abuse of his body makes him old.
Tiger is the same as Kobe, he has played so long and so much that his body is old for his age. His swing (prior to the injuries) played havoc on his knees. When he was 22 I told a friend that Tiger's knees would never hold out till he was 35 if he didn't change his swing. I think we will see Tiger around and he might compete for another title, more likely a PGA or a Masters. I don't expect him to do well in the British or US Opens in the future. He might have 1 or 2 more majors in him but not 5 for sure.