Honestly I think Nintendo has both Dragon Quest and Monster Hunter locked up pretty tight for Japan.
The 3DS as far as Capcom is concerned is the successor to the PSP and DS, it's the only handheld that's relevant in Japan, and MH is not big in NA/Europe (not that Vita is exactly doing great there either).
I think for Japanese publishers they'd honestly rather just have one dominant platform. Having two divides audiences and I don't think many Japanese devs even want visual fidelity beyond the 3DS because it would raise development prices and cut into profit margins for handheld games. Handheld games in Japan generally go for 3800-4800 yen, versus 5800-7800+ yen for many console games ... keeping handheld dev costs low is a priority for sure as the profit margin is not as large.
