Yes they cause boosts upon release but with each new installment the impact is lesser. Here are 3DS sales in Japan for each Monster Hunter game.

Monster Hunter 3G-365k

Monster Hunter 4-284k

Monster Hunter 4G-258k

the week of MH4 was less than MH3G despite 3G being a 2 year old port of a Wii game while MH4 was a brand new original entry. The week of MH4G was less than MH4 despite New 3DS releasing the same day.

There is really nothing to suggest 2016 will be better than 2015.

I don't think it will happen...
Japan has the perfect lineup, but I can't see the West suddenly jumping on...
I can't see a new Fire Emblem installment convincing anyone to get it...
Federation Force certainly isn't going to make it happen...
I would imagine anyone who would get a 3DS for Paper Jam has probably already been convinced by another Mario game...
Same could probably be said for Bravely Second...
Perhaps if Pokemon Z happens...

Yeah, for sure. I think 3DS is on its way out and Nintendo will more than compensate for that.

Hardly, but maybe with price cut.

It could, but it won't, because 2016 will be the year of PS Vita resurrection.

Honestly, I don't even think a price cut would do the trick, even if all the models got them across the board and they were all $30. Hate to say it, but the end is near for the 3DS, 2016 is its last ride.

No.

In the west nothing will replicate the sales of the new 3DS hardware release. Most of the late to be localised titles (FF explores, Project X Zone, Bravely 2nd) will do little to nothing for 3DS hardware imo

In Japan 2015 has actually been pretty strong with Yokai Busters, Monster Hunter X, Zelda Majora's Mask, Animal Crossing, Zelda (the other one), Fire Emblem etc. The only big differences is that 2016 will have pokemon Z, I don't think that will be enough to offset the 3DS's natural decline.

Since Nintendo is garunteed to at least show off the NX in 2016 its hard to imagine the 3DS sales not being hurt by an impending replacement with a face and release date.

Well, if they do reveal the NX this year, they'll have to make a pricecut if they want to get rid of all od their stock.

I don't know at all, everything could happen. Pokémon Super Mystery Dungeon this november in North America could do an impact and then in Europe (try to release it before April, Spike Chunsoft). We shouldn't forget Hyrule Warriors Legends, M&L: Paper Jam Bros, Fire Emblem Fates, Metroid Prime: Federation Force, Mario & Sonic at the 2016 olympic games... A new Kirby game that HAL should be developing during at least one year...

Its very difficult to predict... But the system will overcome the 60 million for sure... 65 million has still a chance... 70 million is quite hard actually.

Oh Yes - if they can add a couple of more games tehn sales can be similar to 2015!