Wasn't there a rumour that JK Rowling was not really keen on them and wanted to see them go anyway?
I've seen this rumour a few times too, apparently Universal managed to convince her to keep them due to budget reasons. If it is true then this was always going to happen at some point.
I really hope Universal develop the plot of land in a smart way because the footprint of Dragon Challenge is HUGE. I wouldn't actually be surprised to see them use it for not just one addition, but maybe a couple of additions (2019 and something else in the long run).
Same, I'd be shocked if we only see one attraction take over this area. Excited to see what they do as their Potter areas are incredible.