I agree it's unlikely, but that's the sort of sales the PS4 needs eventually to be able to sustain itself as a platform. If people aren't moving over, then it will continue to hold publishers back from committing to current-gen for anything other than games which require the highest technical specs. Since we're talking about Japan, there aren't many of those!
If DQH ends up selling 500-600k on PS3 and 200k on PS4, and MGS5 does the same, that is unfortunately not a very encouraging outlook. The important thing about these few months in Japan is that there are a lot of PS4 titles including Bloodborne, and there are more on the horizon. If people don't jump on right now, then it's likely that there won't be another big window of excitement for a while, maybe not until the end of this year or early next year.
No, wait, I thought you were meaning first week, not LTD...
Absolutely 300k LTD for PS4 version is doable, in the next weeks the userbase will grow up rapidly, but considering the huge difference in userbase between PS3 and PS4, I think it's hard to see both versions selling the same or similar numbers (and I mean a tie ratio less than 2:1)
Around people jumping on the ship, as I said some page before, the games which can give a real boost to sales are BloodBorne and FF Type 0, which are exclusive to PS4 and not multi with PS3 (ok, Type 0 is also planned for XB1, but who cares?)
So I consider more important the result of that couple of games than DQH or even MGSV, in the short time obviously.
In the second half of the year I presume the gap in sales between PS3/PS4 games will gradually decrease and for that time I hope to see more PS4 exclusives and less multiplatform titles.
Ok people might be lazy to jump on PS4 but also publishers have to put an end to PS3/PS4 titles, giving to the customers a good reason to buy a PS4 and forget their lovely PS3.