Replacing more bigger harddisk

Is it possible to replace the standard 1Gb wdtv live hub hdd with a newer and bigger (2 Gb) hdd?

No, as far as I know, 1TB is still the largest 2.5" HD available.

OK, how about technically speaking, let’s say my current WDTV Live Hub is now full and I don’t want to add more space by using external hdd thru USB, I just want to simply replace the internal hdd with a new fresh 1TB hdd, is this possible? (I also don’t mind if I break the warranty).

Sure you could swap the hd, as long as you replace it with the same brand and part #.