OK, time to don the Sherlock Holmes cap and analystigate this thing! I've just come back from seeing the proposals in person and would like to report back!
First, let's focus on the animals. On the master plan, area 10 is listed as area for animal enclosures or an overflow car park. In fact, the staff member I was talking to even mentioned the possibility of moving the entire zoo into that one area of the park, leaving room in the current zoo area for new rides and staff facilities and connecting Zufari and Wanyama with the rest of the park. When I asked him about what effect that would have on newer attractions in the area such as Trail of the Kings, Amazu and the penguins, he responded by saying that it would depend on how far down the line the redevelopment were to happen and how big of an investment the replacement was to be. It's also possible for animal enclosures to be moved to other areas such as the picnic field where the new coaster is due to go, with the new ride going elsewhere.
On the subject of rides, the reason why the new for 2016 ride was cancelled was, as expected, due to the budget being moved to general park improvements such as what has been seen over last closed season. The plan does seem to be to add smaller new rides such as these over the next few years although he didn't know if those exact plans would be brought back from the dead.
In the pdf file, you can see 3 concept images for rollercoasters; 2 for what appears to be a jungle/temple-themed launched motorbike ride with the trains restyled to resemble a quad bike and one for a pirate-themed water coaster. I mentioned to the staff member that I had issue with another jungle theme being included and seemed to share that sentiment. He seemed to be a big fan of the water coaster idea, although I mentioned, as others on here, that the park does already have a few quite good water rides. I pointed out a part of one of the concept images resembled 13's drop track section and although he wasn't part of the marketing department so couldn't know for sure, thought that I was most likely right.
One other interesting tidbit I heard at the event was that since the "relocation of thrill rides to Thorpe Park", the visitor levels per day have been rather stable although noticeably lower, and that the park hasn't been over capacity at all, whereas previously the park has had to turn guests away frequently on busy days, causing problems with traffic. If the new additions were to increase guest numbers, I'd imagine that it would be small enough that the extra capacity gained from the additions would offset it enough to not cause any issues.
I think that's it. All the other bits I remembered were local residents complaining about traffic and green belt land, but if someone mentions something on here I'll probably remember something else to mention.