Square Enix pays their staff like any company a sallary or hourly wage
no shit?. Them having more money isn't going to suddenly make them want to spend it on the game
...yes it will..., it's just going to boost their bottom line.
as will putting more effort into an ongoing game that costs QUITE A BIT LESS than a new IP or another FF(we all know how well that went recently)
Unless Square Enix is hiring new members for the development team
more money means they could, the exact same ammount of work is going to be done on FFXIV today as it was tomorrow
OR MORE! 
, the operating budget will likewise remain the same
or it could be higher, likewise anything expensive like moving servers wont be looked at until the companies next budget meeting and trust me that "Cash shop revenue" is not in a collum of the spreadsheet the bean counters will be using when they decide if moving the servers to EU is a profitable move for the company.
The EU data center will happen only if and when SE feels they would gain more customers than the cost of implementing the data center would cost, not a single thought will be givin to how much cash shop is generating comes into that decision.