I would hope Enterprise is the next to go, after what happened to Thorpe's and just the general state of the thing I would be nervous to go on it again.
The Flume doesn't need to go, it has massive potential. I mean, it's a water ride that's right next to an area with a theme very strongly associated with water! If it is rethemed it has so much potential for an incredibly immersive attraction, they could have theming in the currently totally bare forest-meander-y bit between the first and second drops. On the last drop you could pass through some sort of pirate themed structure at the top, possibly with a flag or sails on? Then of course you could have loads of fun with the main like, little pirate ships floating around, firing little smoke puffs every now and then...
I got carried away there a bit... but I agree with the above posters, something to replace the Beastie is sorely needed and it'd be one ride where AT wouldn't have to worry about height restrictions!
In terms of coasters, I think Corkscrew was the last "off-the-shelf" coaster to leave the park. The rest are custom which I imagine will stay for a long time.