Two or three more winters may come before a "Game of Thrones" prequel premieres on HBO. It is known.

"Game of Thrones" Season 8, the final season, is now filming and will keep filming into the summer. It was recently confirmed by HBO that the six episodes won't premiere until 2019. Keeping that date in mind, it means none of the planned prequel spinoffs will arrive until at least 2020.

As you probably remember, there are five prequel series in the writing stage of development. Those prequels will cover author George R.R. Martin's stories set before "A Song of Ice and Fire," the novel series upon which "Game of Thrones" is based. GRRM is working with all of the writers on what he prefers to call "successor shows" rather than spinoffs or even prequels.

HBO programming president Casey Bloys gave The Hollywood Reporter a spinoffs update during the recent Television Critics Association's winter press tour:

Let's start with the Game of Thrones prequels. What's the latest?

There are five of them. If we do a pilot and series, nothing is going to air on HBO until at least a year after the final season. We're not doing a final season and then, "Following it at 11 p.m. ... ." I've seen some exciting material. We have really great writers working on these; it's very exciting. But there's no timetable. Not everybody is on the same schedule, so I've seen different versions of different things that are potentially exciting. But there's no timetable about when a decision would be made about any of them.

Can you discuss any of the storylines that are being explored?

No!

In success, do you have an idea of just how many you'd do?

I'll do anywhere from zero to five! (Laughs.) Though probably more likely one. But we'll see.

Bloys further confirmed to TVLine that no existing GoT characters will be featured in the prequels, but there may be familiar bloodlines -- meaning members of the great houses we've come to know.

The HBO boss did previously say that "Game of Thrones" is the priority, and they won't do much of anything on the spinoff front until that series is done. So that's why they don't expect any one of the potential new series to show up on the network until "at least a year" after Season 8. It sucks for us, but ... at least we can look forward to something once GoT withdrawal sets in.

Want more stuff like this? Like us on Facebook.