1. How many provinces are there and what are they?

2. What is the size of Tamriel?

3. Is the emperor we meet in Oblivion emperor of Cyrodiil or all Tamriel?

4. If TES V is set in a province we haven't seen before, will there be new races?

5. Are there any races who were not native to Tamriel?

Thanks guys.

god-of-madness

1. Nine provinces. And I dunno really what do you mean by "what are they?"
http://www.uesp.net/wiki/Lore:Tamriel

2. It`s large

3. He was emperror of Tamrielic Empire, not only Cyrodiil, which is seat of governance.

4. Probably not...

5. Yes, you might want to read more about land of Akavir
http://www.uesp.net/wiki/Lore:Akavir
It can be noted that Dragons come from there, and therefore they are not native to Tamriel

Edit:
Small adnotation to point 5.

Redguards (in their own language 'Yokudans', taken simply from the name of their homeland) hail from the western continent of Yokuda, which sank into the sea in ancient times. The cause of Yokuda's sinking is attributed either to natural factors (such as earthquakes, tsunamis, and volcanic eruptions) or to the sword-magic revenge of a defeated band of Ansei called the Hiradirge. Upon the sinking of their homeland, the Yokudan fleet set sail to the east, eventually landing in Hammerfell.
So in some way they are not native to Tamriel either.