It opened in 2003 if I remember my dates correctly, but I'm now unsure if the ride system was new or not. As said earlier there is some old jungle theming remaining (Very lazily) from a past ride. From what I can gather there used to be a ride there called Jungle Cruise, which was also a tow boat ride it seems. Was it the same ride system? Or was it all stripped out and a new one installed for 2003?
If the ride system was new that makes it less than 10 years old. It does really make you wonder what could have gone so horribly wrong on the ride that the park may feel the need to remove it. It's a tow boat ride, hardly something incredibly complex and overly engineered
Aside from the themeing the only bit of the ride which ever really seemed to have issues you'd notice was the audio. Though I think that was more down to the way the audio system was actually designed and set up than the actual ride's fault.
With a bit of investment both Excalibur and Pirate Adventure could be turned into two first class family rides. There is massive potential with both rides, but since opening it seems both have gone rather forgotten. I mean even if the park just invested in repairing the animatronics around both rides, using newer more reliable technologies it would be a massive improvement. It's not like they have anything massively complex that would cost a fortune to do.
With some money thrown at it Drayton could turn Pirate Adventure into something on the level of DVH at Efteling with regards to themeing. There's no shortage on space in the building.
One of the things I loved though were all the small details in both rides which made them humerous. These little details can make a ride for me sometimes. Excalibur had a good mix of humour. Some that children and younger guests would understand, and some more mature, and even rather dark in places, comedy that would go straight over their heads, but make most older guests laugh.
If it does go I'd be very surprised if the park tried to install a coaster over it. That lake is a fair old size, and it'd be a shame to see it go to waste. I can see possibly some form of interactive water ride going on it personally. UK's version of Wakobato maybe?