Not really since Vita isn't as expensive as it is on console. There's a reason why SOJ started to concentrate more on handheld systems with their various games as well as platforms on their way out before they fully went gung ho on the digital side of things. They looking for the least minimal R+D costs to reap maximum profit.
What makes game content on Vita more expensive then game content on PS4? Aside from graphics cost of course, I mean of course most games on PS4 are going to have better graphics. I'm talking about publisher fees and such. Do you have any proof you can share?
I have done some research, and while most info seems to be behind locked gates that require you to be a developer and sign NDA's... I did find this bit.
When it comes to working with third party studios Boyes said "it's talking to them directly, it's listening to them, it's caring about what they have to say and then it's actually taking that feedback and actually applying it to improving things."
Describing developer meetings as being "like a focus test" Boyes commented that Sony try to take what they learn from these meetings to make their consoles even more developer friendly. One way in which they aim to do this is by waiving fees for making game patches in the majority of cases.
"Our publicised policy is that you have to pay patch fees in order to patch the content but the reality is, especially for independent developers, we don't charge them for that. We have not in the last three years in our territory. It's really important for us to work with them to make sure it's as early as possible for them to get the content out there, especially if it's a fix for a game breaking bug," Boyes revealed.
http://www.gameranx.com/updates/id/13654/article/sony-on-developer-relations-and-waiving-game-patch-fees/So that makes me curious. I imagine Sony waives update fees if you make some kind of deal with them. I mean we have no way of confirming since we aren't the ones working on PSO2, but SEGA seems to have no problem with the game being on PSN, as it's on the Vita. Whether it's on PS4 or PS Vita isn't going to make a difference in regards to patch fees. I also imagine Sony realizes it is common knowledge that MMO's need to be updated often and aren't going to charge a rediculous amount for patch fees. Seeing as how there is a lot of other MMO's on PSN I can't imagine the fees are that bad or if they even exist at all for MMO's.
As for if Sony gets money from DLC that is irrelevant in this case, as the only way to purchase items with real money in PSO2 is to buy an in game currency through SEGA's PSO2 website. This is true for both the Vita and PC versions.
PS4 also has PC architecture, so it wouldn't be very hard or super expensive to port or anything. I mean of course it would cost money, making a port of any kind does, but if it has potential to greatly expand the userbase, then you take the risk and make the port. Game development in general is all about taking calculated risks to make a profit.
With those facts in mind. I don't see any problem with there being a PS4 version.