SPOILER ALERT
Just so you know...
1. Snoke isn't dead
The same way that Luke was able to project a younger version of himself across the galaxy, I don't think the slightly healthier-looking Snoke was actually him. This is already a popular theory, so I won't really get into it that much.
2. The next flagship of the First Order
With Snoke's flagship destroyed, I imagine there will be another, and I think I might know what it is: the Super Star Destroyer "Eclipse." It was confirmed to be canon in some novel (forget which one) and under the command of Grand Admiral Thrawn on the outskirts of the Unknown Regions. I suspect that Snoke's actual form is somewhere near this region, so it seems likely that the Eclipse would be the next big weapon of the First Order despite being a relatively old design. Maybe Thrawn will make an appearance.
3. Foreshadowing
The end of the trilogy might hint at the next plot concept. What could it be? I really hope it's more original than a third Empire versus a third Rebellion. Personally, I hope they reintroduce the extragalactic Yuuzhan Vong as the next major antagonist force. Like Thrawn and the Chiss Ascendancy, they're too big of a Legend to just leave out altogether.