One of the biggest reasons only some 3DS games are on the eShop is that Nintendo only just started putting retail games on there. We may see older third party games come on there like we're seeing with some of Nintendo's own older titles, but that's going to depend on the deals Nintendo can make with third party publishers. I think the extent to which we will see this happen depends on how well the new games that come to the service do in terms of sales. The better those games do, the more likely we are to see more games available that way, both new and old.
As for the CPP XL, I doubt they will bundle it with Monster Hunter, because it would be useless for people who own the original model 3DS instead of the XL.