The Japanese are smart people. They see rising threats in their region, and they also see Trump pushing NATO to pull their own weight in theirs. The handwriting is on the wall, they need to do the same, and Abe is stepping up.
Even the discussion of this puts the Chinese on notice.
A problem here is that as Japanese military capability grows, there will be increased pressure here in the US to “let them (Japan) take care of it” (whatever “it” is), and as we draw down our forces, that in turn forces Japan to attain even more capability. At some point, if Japan thinks the US is not a reliable ally (such as whenever some leftist gets into power here), they will have no choice but to go nuclear.
Now, something to keep in mind is that despite present business ties, there are deep hatreds and suspicions in this region. If the US bows out of the region, IMO you get a major nuclear war. It might not happen for a few to several decades, but I think in the long run it is almost guaranteed. Maybe some fools think this would not also be a disaster for the US — they are horribly wrong, even if we are not drawn into the exchange...
The above also neglects another likely factor: A militarily strong Japan might well over time drift away from being a US ally. I will just leave it at that...