The short answer to your question is that yes, he will have opportunities to play in many different positions throughout his youth soccer journey as long as he sticks with it. There are plenty of very tall forwards and strikers at the upper levels of the game.
The more complex issue has to do with how youth club soccer works, the types of coaches he will run into, and what happens after puberty. The worse a youth coach is, the more they are focused on winning meaningless U10 games, the more they will rely on the size and physical traits of their players to win those games. (I'm surprised your son wasn't asked about playing in goal if he's that tall.) But after puberty starts to hit, the balance of size and speed shifts among his peers, and suddenly kids that used to look huge on the field now aren't so special. Your kid might be tall relative to the average now, but that could change in HS. Or it might not, especially if you and/or your wife are very tall. But regardless, you should be cautious of youth coaches who are overly fixated on how naturally big, strong, or fast a 9 year old is. To me, that says they don't have a big picture, long-term mindset. They'll do things like always put the fastest kid at striker or wing, or always the tallest kid as center defender, or always the biggest, strongest kid in goal. At 9, the only reason to do that is to win 9 year old soccer games. A coach who is willing to move players around teach them all skills regardless of their current physical stature is a coach worth finding. Don't let your relative ignorance of the sport as a newcomer make you put soccer coaches on a pedestal and think they know more than they do. Take it from the veterans on this board: club soccer is an ego magnet for people with failed athletic careers and unfulfilled soccer dreams, both coaches and parents. Be wary.
Another point which has been made by others in this thread already is this: embrace playing defense at a young age. In college and HS, a field player who can only play one position is a liability. And it is much harder to take a kid who played forward all the time as a youth and teach them defense than to take a good defender and teach them attack. Players who learn how to defend early on are SOOOOOO much better off than vice versa. There is a point at which the knack for scoring goals will naturally draw a player over to the attack side of the ball. So if he plays defense now, and is good at it, but still shows an ability to put the ball in the back of the net, he'll be a coaches' dream.