The assumption is that you will get EOS tokens for your 'temporary ETH-based EOS tokens' once they are made.

However as several people have pointed out, the whitepaper actually does not guarantee anything. Others have also pointed out again, that this is not uncommon since during development anything could change and it would be bad for the devs to lock them down to anything.

I guess it depends on wether you trust the team behind EOS or not. Make your own risk assessment.

How the actual process of getting the 'real' tokens will go is still uncertain and will probably not be made known until the 'real' tokens are near completion. I imagine the news will be widespread on how to do this, once it is possible. Hope that helps!