It's naive to dismiss the possibility that the current acquisition-heavy climate will negatively affect Nintendo in the mid to long term but the most recent moves (Zynga, ABK etc.) do not, at least not directly. Most of Nintendo's success still rides on their own games and that isn't going to change any time soon. It will become a problem once someone makes a move on their large development partners, most notably Bandai Namco and Koei Tecmo. I suspect this is part of the reason why Nintendo is preparing to invest a lot into expanding their own development capabilities: So they can be less reliant on these external studios. Their internal teams are still responsible for most of their most successful IPs and ideas so it makes a lot of sense to strengthen them in various ways. I think we're going to see more of what is already happening: More internal expansion and stronger co-development efforts between their own teams and partners like Game Freak, HAL and IntSys.
As for mergers and acquisitions, I don't really think they're interested in anything even approaching the scale of what we're currently seeing from these other corporations. Fiendcode posted this list on Install Base when Zynga was acquired (Market caps in $):
Activision: 49.88B
EA: 37.27B
Take-Two: 18.98B
Embracer: 10.56B
Ubisoft: 5.35B
Bandai Namco: 16.35B
Konami: 6.57B
Koei Tecmo: 6.31B
Square Enix: 6.26B
Capcom: 4.75B
Sega Sammy: 3.67B
Nintendo: 54.53B
Activision is obviously out. EA and Take-Two after the latter gets Zynga will be too expensive. I don't think the owners of Embracer and Ubisoft want to sell and they'd be too unwieldy anyway (12k and 18k employees in several locations respectively, compared to Nintendo's ~6500). This takes the first half of this list out of the equation.
As for the Japanese companies, there's probably a combination of the owners not wanting to sell and/or the cost outstripping the benefits. It's not like Nintendo can drop a cool 5~10 billy just to buy a publisher if that money can be put to better use. Does it make sense to spend this much on a company like Koei Tecmo which has no notable IPs?
Some of them also have ancillary businesses that Nintendo has most likely no interest in and would have to be divested. Not sure what the current numbers are but almost half of Konami's work force used to be employed in their Sports subsidiary which operates fitness clubs. Sega Sammy could be interesting but what do you do with the PC business? etc. Bandai Namco has been leveled as a potential merging partner but it would take some time to align all the various branches. If Nintendo wants to get into toys and merchandising in a big way, this would definitely be the way to do so. They're also quite big though.
Investing more in Japan might also be a bit overkill when they're the de facto market leader in the console business with no sign of that changing. I actually think that Capcom would be the publisher with the best cost-benefit ratio for that reason: Resident Evil and Monster Hunter are very successful series that Nintendo fans have a lot of affinity for and they're both popular in the West where Nintendo has a (comparatively) weaker foothold. Add to that Street Fighter and the rest of their deep library. But again, not seeing the Tsujimotos being particularly interested in this.
I still think we're very far away from large M&As becoming a necessity for Nintendo but I'm less certain than I was just a few days ago. In the last two weeks we saw the two largest gaming acquisitions
ever. Microsoft is spending more on ABK than Nintendo's current market cap. It feels like nothing is completely off the table right now. Question is, how fast does Nintendo have to act? What has to be done through acquisitions vs. organic growth?