This basically. The crossplatform ease of development (handheld -> console and vice-versa) is a big point to attract Japanese devs/pubs in the future.
And yeah, as said before, power just isn't enough to attract western AAA content on Nintendo platforms, sadly.
I think it's a little premature to say this with certainty.
Why is Persona 5 a Sony home console exclusive even though the best selling game in the series was on Vita? Why is Dragon Quest seemingly returning to Sony home consoles as a multiplat, if not a downright exclusive when Nintendo has the only relevant dedicated handheld in the business? Why have the 3DS and Vita only seen token support from Square-Enix so far, even when compared to the Xbox One, a platform that is more or less irrelevant in that market? Because Japan is just not all that important anymore.
As the dedicated gaming market in Japan continues to decline, developers are turning their attention towards the West. Case in point; several Japanese third parties have mentioned how the PS4's popularity overseas encouraged them to greenlight several projects for the new consoles. At this point, having a successful platform that is conducive to the type of content Japanese third parties want to create in the West is arguably more important to gain their support than one that built with the Japanese market in mind.
Sure, easy cross platform development between handheld and console would be huge for Japanese third parties but only if both form factors become relatively successful. Otherwise, what's the point?
With home consoles becoming a niche in Japan (and are unlikely to break out of it barring a major shift in consumer behavior), it all comes back to building a console that will be embraced by the West. Which means developing first party exclusives that make a difference in the West (high-profile IPs with a more realistic presentation) and mending relationships with western third parties to bring their popular IPs (FIFA, Madden, CoD, etc...) back to the Nintendo ecosystem. Decent marketing would go a long way too.
If Nintendo aren't willing to do that, all they can reasonably expect from Japanese third parties, even if they manage to cook up an excellent cross platform solution, would be a cross between the 3DS and Vita's current libraries, if even that.