Neverthere
I think your fears and question are valid. We hear a lot about abuse running in families and the idea that victims become abusers.
Well yes there is a proven inter-generational transmission of abuse. That has been well documented. It occurs when one family member preys on another. Both learn this as a way of life. The victim grows up and feels most comfortable with a way of life that is familar - dysfunctional. They wind up being involved with someone else who came from a dysfunctional family. Together they create another dysfunctional family and often their children become victims who grow up and repeat the pattern.
There are two things required to break the chain. Remove yourself from the dysfunctional family system and get counseling to make sure you don't get back in another one and undo the damage done.
Well you have taken your child out of the situation and are providing a safe home. That is the one step. The second step is harder.
Even though your child may not talk about what happened (and he probably won't) it often comes out in their play. Therapists working with child victims often use play therapy to help these young children express how they feel about what happened to them and help them to overcome any long-term effects.
I would suggest you watch him closely while he is playing. See what comes out. If it sounds healthy. At his age he will be experimentling with "playing doctor". You will have to have nerves of steel if you catch him. Let him know his interest is normal but he can ask if he wants to know the differences. Also watch that if he is playing doctor that it is simply "I'll show you mine if you show me yours". Any thing that involves overt sexual acts that a small child would not know about unless they had been exposed to sexual acts are major signals that it does indeed affect him.
I would certainly recommend talking to a professional who deals with child victims
And it is a myth that all victims become abusers. Look at the number of survivors here alone who have grown up to protect and defend children. It is true that some do become abusers but I suspect it is the minority. Teaching children that power is something within them and not something taken from others is an excellent way to help a child grow into a responsible caring adult.