Well, the only reason we think this is a problem is because there is only one other 2 UMD PSP game, and that's Sora no Kiseki Second Chapter. Falcom's older PSP games are all on PSN now except for that, and they stated that it was because they had problems getting it onto PSN because of the 2 UMD format. It's possible that they simply did not program the game with this in mind and it would be too much work to modify it to work for PSN.
On the other hand, S-E is developing this game while fully aware that a PSN release is expected, and would indeed be required if they want it to be playable on the next generation system. If the game does not end up releasing on PSN, it will mean that 2 UMD games are indeed a technical problem for PSN. Otherwise, it just means Falcom did not develop the game with PSN in mind.
We'll have to wait and see.