I would not base any buy/not buy decision on information like this :)
The memory savings are mostly in better handling of scene geometry, so if most of your memory is now taken by textures, you will not see much benefit from this particular optimization (although we plan to optimize texture memory usage as well).
From my experience, any additional RAM is never wasted. It will just allow you to make bigger scenes, higher resolution textures, higher resolution renders, etc. :)
And yes, we'd like to do the first v5 daily build quite soon.