Given that about 0.5% of the population are trans, it should not surprise us if about 0.5% of children will grow up to be trans.
How many of that 0.5% will figure it out while they are children, and tell people, versus how many will either not figure it out until they are older, or keep it to themselves out of fear and shame etc, is another matter - but it makes sense that as trans issues become more discussed and visible, more kids may come out as trans.
This is really not all that different to kids realising they are gay. If, say, 5% of adults are gay, then it follows that about 5% of kids will grow up to be gay. Some will realise at an early age and some will not. Of those who do realise, some will come out early and some will not.