Tales of can be on any system, there is no guarantee the next major one will be for PS4, if I were Bandai I'd target PS3/smartphone. Biohazard interest in Japan has been in decline since Capcom turned it into western bro shooter. Ryu ga Gotoku could probably sell a couple PS4s, but the next one will likely be cross generational again. FFXV is vaporware, and IF it ever comes out, it will be so late that it won't help the PS4 much. FF games generally don't. It can bump up the numbers a bit, but they are so front heavy, that if there isn't the stock, it can't move them.
Yeah, I don't see them having much of an impact. If MK8 can't improve Wii U sales by much, why would people think less relevant games will for the PS4?
There is a shelf life. If the PS4 takes too long to become valuable enough to purchase, it won't ever. Every day it waits, handhelds get more powerful and the PS4 looks more expensive. They will probably have to do a price cut even before there is anything worth buying at this rate.
I don't see Namco making a mainline Tales on smartphones at all, but they already have made a few smartphone spinoffs. If Namco makes another Tales on PS3 I could see a Zestiria 2 reusing assets, but I don't see another Tales with a brand new world. Tales is most popular on Sony consoles, and after the PS3 is the PS4. And I don't think I'd say the next Yakuza will be cross gen is likely...
Even with MK8, the Wii U is lacking notable third party support, and even the current Nintendo lineup might not be enough yet. Not that the PS4 situation is much better at the moment, but it's still the go-to for JP third parties wanting to make a console game.
Your "handhelds get more powerful and the PS4 looks more expensive" doesn't make much sense. Any new handhelds that are going to come out are going to be expensive. Even if they're priced similarly to 3DS/Vita, at the same time the PS4 is going to have price cuts. So no, the PS4 isn't going to look more expensive. The price can only go down.
Also there's not much reason to cut the price if there are no worthwhile games. It's not just a price issue.