Epic Games recently announced that the minimum requirements for Fortnite will shift for PC users. It is not a big deal since it will simply no longer support super old GPUs - the game will ask for a DirectX 11 compatible card now.
Epic Games stated they have been supporting even older cards with DirectX 10 in Fortnite for a long while, despite the system requirements listing DirectX 11 compatible cards as a minimum.
Players who used these older cards should have plenty of time to react and upgrade their hardware because they have at least over one month worth of time to do so. The company didn't announce Season 10's start date yet but Season 9 will conclude on 1 August 2019 which is already plenty of time to change the GPUs.
Just in case you were wondering how much it would set you back to meet the minimum requirements again, the GTX 660 costs around $150 these days for some reason but we wouldn't suggest getting one if you are looking to upgrade.
GTX 1050 can be found in a lower price range and offer a bit better performance than the 660. Meanwhile, GTX 1050 Ti should be available in the same price range and this card will offer much better performance in general.
The AMD equivalent would be AMD RX 570 which can be found in roughly the same price range and is generally more bang for your buck but differences in Fortnite performance will be just about invisible.
In essence, if you have a really old GPU, Season 10 will require you to change to a slightly less old one or a fairly recent one that happens to be in the same price range.