The old lady was, by all accounts, completely antiquated and inadequate as a modern office space and the cost of renovation seems to have been more than it was worth; with a move to Tara Street (where I assume they are leasing the new building) being the more economical option.
So what does this mean to the average reader? Probably nothing, at least for the time being. Things will seemingly carry on as normal, but perhaps the new surroundings will help give the staff the moral boost that rumour suggests is much needed.
On top of this, perhaps in the not too distant future we will see a more modern outlook from the newspaper, to match its modern building. The Irish Times has always been the one publication most likely to take advantage of a changing media landscape, and perhaps now they have the improved facilities to do this properly.