So does this new wallet reduce the ram usage?
no, that problem is more complicated and since it doesnt actually change the chain. i still havent found a long term solution for that.
the 4.0.0 wallets have about 100k more blocks before they will no longer function and will fork. so we will just need to find someone to compile a mac wallet before then.
the memory wallet will come out as 4.0.2 and will be an optional update