Obviously, OP, your DC is a product of your and your DP's gene pool, but that combined gene pool will include earlier generations with very different personalities, strengths and weaknesses.
Added to this, the environment in which they are growing up, and the sequencing of any experiences, is different from yours, your DP and that of any siblings.
So the range of possible outcomes is very wide. Clearly it can be influenced by parents but also by DC themselves; the latter is a really important aspect, in my view, and more on this below.
Developmental progress is often very uneven and not at all linear. Better to have a parental mindset that embraces that than seeks reassurance that a DC should be, and is, and will remain on some kind of smooth academic conveyor belt (OP, I am not suggesting you are thinking this but it is a potential pitfall).
I am also an Oxbridge graduate but did not come into my own in any shape or form until Y9, so one really cannot make concrete assumptions in earlier years (and one of the reasons I think 11+ and Grammar segregation is flawed).
I live in an area with no Grammar schools (true of huge swathes of the country) but sending my DC to a comp (average; very mixed socio-economic catchment) was an active choice. Dynamic setting enabled them to bloom in areas where they had potential, crucially at the right pace and time for them.
Additionally, and much more importantly, I would say they gradually built up skills in resilience, self-reliance and self-direction which, I can see, is standing them in really good stead in the years after school. It is that I focused on as a parent, rather than worrying about performance comparisons with DCs' peers. So, in that sense, the question posed by the OP is an interesting one, but the wrong one in my view.