Well here's the thing: We don't know exactly when we will get said update. We likely won't see it for a while, and luckily our friend Daiske made that clear, which makes sense since a system like that would require a large amount of content to already be out. It would be pointless to have that system with what we have currently because it would be half of a system and some of the ninja they have in said update would be permanently locked behind walls that need some future ninja first.
As far as saving goes, I would say it wise to just wait out the update for now because you never know who will come in future updates to shop and who will become cheaper. I think its safe to assume that in our first one we will likely keep all that we have now and some will become cheaper. Personally, I'm saving all of my coins for the update just to see and intend to go wild with them as soon as it is released. Of course it's a bit of a gamble because if we do lose anyone I might miss out a little but, then again, this whole game is a bit of a gamble when it comes to ninja. :p