#1

Depends on a lot of things and there's no real planned release date. My guess would be between March and April. Note that you can already play with some of the new features in the Windows 10 edition. That already contains bamboo, panda's and scaffolding.

#2

No, but it does depend on your needs. Random spawns will happen no matter what, so eventually you will see foxes appear and may even come across panda's. However, you won't get any new biomes (so: new areas) within your "known world". So: the area which you already explored and which got generated.

Don't expect bamboo to suddenly appear in a jungle you recently found.

So to get to the new stuff you'll have to travel further outwards within areas that haven't been generated yet. Then you may come across new terrain with new features.

A fair warning though: this is most often not good for consistency. The world generation routine often gets updates which means that there will be differences in the way a world gets generated between versions. Ergo: it is possible to walk into a desert and then see that immediately turn into a polar area, including polar bears ;) Not very realistic, but ...

So for the best results it's usually better to create a new world.

Thank you spygron, so propably not necessary but recommended.

I don't think you will have to reset your world for the new update, but I think you miiight if you want the new biomes.