A common misconception I would like to clear up here is that, while the word 'new' implies that everything will be changed, the old FFXIV and the new FFXIV are essentially the same games. The battle systems already in place and will be in place in the future, Grand Company, etc... it is all the feedback we've received from the playerbase that be used and be reflected in FFXIV is what I call 'new'. But on the other hand, when we do switch over to the new FFXIV, you can say that from a developer cost standpoint that some of the time we've dedicated into the old FFXIV will be wasted.
Take the UI, for example. Under the new FFXIV, the UI will be totally revamped and be replaced with the new UI engine. However, this doesn't mean that we're slacking off in improving the UI we have now lest we make our customers feel unsatisfied with our product. Therefore, we will continue to make improvements to the current UI by reflecting on customer feedback, and continue to provide updates. Things like that won't change.