It depends on the format of the ebooks avaible on a Kindle. It seems that you can view PDF in Tamil on a Kindle, but not the mobi format which is the stardard format for amazon ebooks. So you will be restriced to the books as most ebooks on Kindle are mobi format. However, this may change as there are over 66 million people speak Tamil as their mother tongue. There will be the demand to make mobi compatible with Tamil, one of the oldest language in the world.