GoT has, at the last count I saw, four successor series under development at HBO (down from a peak of five, and likely but not certain to get down to only the best actually getting full-scale production), with one already, unless I missed a schedule change, already filming, with the showrunners of GoT and GRRM all involved in all four.

> Content of the same quality is much more available now than when GoT started running.

I don't think that's actually true. It think content of GoT quality is available from almost exactly the same number of sources, in almost exactly the same number of titles, as when GoT first aired, and that's even more true if you consider value to people who would pay $15/mo just for GoT (and even if it wasn't, most of the people who would can afford to pay the same amount more than once if they have another source of equal-quality content available.)