I can proudly tell that Qt 5.10 Alpha is released today.
Please check Qt 5.10 New Features -wiki to see what new is coming with Qt 5.10 release. And as usual the official Alpha is a source code delivery only.
Next milestone in our way to final Qt 5.10 release (which is planned to happen at the end of November) will be first Beta release. We are targeting to get it out soon after the Alpha. We will release several Beta releases in similar manner as we did with Qt 5.9 - made available via the online installer. Each new Beta release will add maturity and improvements based on user feedback.