Here are somethings to think about on this, PS2 limitations, a common phrase for FFXI, this is why SE was saying they want to keep the gaming experience the same on all platforms. Look at ARR "We have downgraded the graphics to run on PS3" that's instantly the FFXI idea out of the window because the gaming experience changes, ie no PS3 limitations.

Ok OP here's an idea for you, PS4 will probably be around £500 - £600 (looking at the initial ps2 and 3 release prices), at this cost very few people buy them, the huge majority wait the 4 months at least for the price to at least half, so if SE chose to ditch the PS3 version for a PS4 release version, they would be saying they prefered to aim the game at about 4 million people over 70 million, tell me where's the logic in that?

Now onto expansions, guess what all they need to do is upload the expansions to PSN, like DCUO did before it went f2p, like most games do with dlc. PS3 will continue to be supported until it is either too hard to support it or the customer base drops to the level it's not profitable to support PS3 any more. which could be 5 years.

Yoshi-P has already said he wants to get the game to as many people as possible, which tells me he will port it to PS4, it's also why they are using a hugely scalable engine.

You also say how "FFXIV was released in PS2's prime" however there is one peripheral that was required for FFXI, which is the Hard Drive, this was such a failure it never made it to Europe, this is why the PS2 version was never released in Europe. Whilst they released it in the console's prime the timeframe to release the game was very small because of the PS2 hard drive.

ARR will probably be a lot bigger on PS2 than PS3 because of that last fact.