IMHO they should keep both versions available, as to make the transition more smooth and in order to test it more. It's still possible to play the old versione, but there is no "public" link.

The new version is too RAM intensive for you? Just keep playing the old version, but without the new features.
Do you want to have the new features? Change to the new one.

I think most people would still play the new version, so there's no need to worry about it's development. Then when it's tested enough and smoothed out you can give it to everyone.