I think the diving bell has been brought up in every single project thread since this site started, not to mention half the other threads in this topic. I'm sure they know about the idea.
For 2015, we're either looking at getting something fairly close to what was pitched in the last set of concept surveys, or they'll splurge and go for a new family coaster similar to Firechaser Express. I'm thinking that they'll go for the refurb of GG in 2015, followed by the coaster in 2016/2017. At this point though I'm hoping they don't go with the fireman theme just because it's been done so heavily at Dollywood. I'm cool with the parks sharing general ride concepts, but I want them to keep being creative rather than recycling themes like Six Flags and Cedar Fair.