That image is very interesting and makes you realise the TP site is mostly useless, once the vacant island next to Swarm has been developed they have pretty much run out of space. Will be interesting to see what they do after that.
To be fair, the park have a lot of spaces they could develop.
Slammer is still SBNO.
The Walking Dead pyramid is almost 30 years old; that will be a spot for redevelopment sooner rather than later.
The beach area (including Depth Charge) could be revamped (even if it's just improved)
The Shark Hotel area was once highlighted as a potential ride development area. If the park ever build a permanent hotel, on the other side of the lake, that could be used
The island behind Swarm could hold a couple of rides
The rapids need a major spruce up
Flat rides are aging, and will need work / replacing at some point
They also have the compound area next to Ghost Train / Trailers scare maze. That area could be used if the park became tight on space
The park have a huge amount of space they could use if they're creative enough, and there's plenty of parts of the park that need redevelopment in the coming years too. Whilst they can't expand the physical land space much more, space isn't something to be concerned about with regards to Thorpe