The PS3's biggest problem at launch was games imo; that's not a problem I expect the PS4 will have. The initial first party support for the PS4 is pretty much guaranteed to be massively superior to the PS3's initial first party support. Sony's first party team has improved so much since 2006 that it's no even worth explaining. This improved first party team obviously will lead to more exclusives at launch than the PS3. This will lead to more sales.
Playstation's marketing has also drastically improved. Do we all remember those creepy white room commercials from 2006? Remember the demonic baby? Sony's marketing was downright terrible at the launch of the PS3 and will definitely be better for the PS4. Sony may not have the perfect marketing strategy, but it's been pretty good since the release of the Slim in 2009. And with news of them hiring new marketing talent, it looks like Sony is focusing on improving even further. This will lead to more sales.
Another big problem with the PS3 was its difficult architecture. The console was so difficult to develop for that almost all multiplats were inferior on the console; many developers even ignored the PS3 altogether. This problem was made much worse considering the X360 was not only simpler, but also released a year earlier giving developers extended time to get used to the system. This won't hapen with the PS4; the PS4 will not release a year after the Nextbox and chances are it won't be as difficult to develop for since Sony themselves said they will be more developer-friendly in the future. This will lead to more sales.
"Given that the successor to the xbox is the true jewel of the eyes of western developers of late, the exception are mostly 2nd party or closely tied to Sony, it's my understanding that most support will ignore the PS4 in waits for the successor to the xbox."
This entire point is probably moot since the Nextbox will probably release this year anyway. So developers will release their games on both consoles. This time Microsoft's console won't have a year advantage though. And even if the Nextbox doesn't release this year, that's going to definitely be an advantage for the PS4 compared to the PS3.
Price seems to be the only point you have, though it's really just a guess. But let's imagine that the PS4 will be the exact same price as the PS3 (which it won't), that point would still be handedly countered by the aforementioned points, so the PS4 would still sell more than the PS3 initially; or at least that's the reasonable prediction at the moment.
Also, the Wii U is much less popular than the Wii. Gamers from the Wii will thus migrate elsewere (tablets, mobile, etc.). Some of them may migrate to the PS4. This probably won't cause any noticeable increases to sales, but Nintendo's downfall is probably more beneficial than detrimental for the PS4.
In summary, advantages for the PS4 include:
1. More/better launch Games
2. Better Marketing
3. Won't release a year after the Xbox
4. Easier architecture (most likely)
5. Will be cheaper (most likely)
6. One less dominating console
