Chill.
I've had the same experience. When I registered, I got a message on screen saying something like 'thanks for registering', and that was it. The website says we'll get a follow-up mail early next week, when we can complete registration. I've no reason to suspect they are lying to us.
But there is nearly a year to go until the race so you'd be nuts to book flights today. Wait another 5 days, then you can book your flight with confidence.
I hope this advice is suitably amazing.