Hum, Ayleids ruins are known to be in Cyrodiil, so if you see a screenshot with an Ayleid ruin in the background, you can be sure it's in Cyrodiil. As said screenshot show no sign of jungle anywhere, then we can conclude that Cyrodiil will be the same as in Oblivion. His assumption seems legit.
That said, I hope that this ruin was an exception and that good parts of Cyrodiil will be covered in jungle.
There will be no jungle, if you want jungle go Elsweyr, thats where the jungles are.
Cyrodiil's landscape was retconned, We need to come to terms with that, and there are a lot more Oblivion players who have no idea that in past lore Cyrodiil was a jungle, so if the MMO makes it into a jungle you'll have to deal with lots of Oblivion fans wondering why they retconned it (and do you really want to deal with the fallout of a recton's retcon? Let's leave Cyrodiil as it is, the current set up will make it fine for the PvP gameplay which will be based there. We will still have jungles, snowy ice peaks, taiga, deserts, forests, plains, mushroom covered ashlands, swamps, and every other biome in-between, I think we can let go of old Cyrodiil, if we cling desperately to every scrap of paper invented for the lore like it's our dying child, then we'll never be able to give this new game a fair chance.