I would have to class such an outcome as "damnably unlikely."
Accepting that the Abe Shinzō prime ministership has been a bit of a stinker, the LDP has nothing to gain and much to lose from a House of Representatives election.
In September 2005, the party stole seats in the urban areas that by all rights should be Democratic Party of Japan seats. The tactic Prime Minister Koizumi used to achieve this act of electoral larceny was brilliant and iconoclastic in the extreme: tell the people that his LDP was running against the Old Guard.
That most of the Old Guard was still in the LDP, even after the rebels were kicked out, was a mere detail. The celebrated Mr. K had a plan to push Japan into a brighter, snazzier, edgier future and no old fuddy duddies were going to stop him.
DPJ leader Okada Katsuya's response to Koizumi's bold play--sticking to promises of fiscally restrictive policies that everyone was already sick to death of, declaring the Postal Reform Law an irrelevant sideshow, campaigning in the guise of a bureaucrat and whining that Koizumi and Takenaka had purloined all the DPJ's best ideas--translated into the Democrats being wiped out in their urban strongholds. In Tokyo, the DPJ went from 12 of 25 district seats to 1. One lonely seat (Naoto Kan's) out of 25.
What is the chance that the LDP could get even close to such a result in the urban areas today? With the prime minister's personal popularity in the 30s?
Damn near zero.
So why would anyone in their right mind (or far right mind, as the case may be) be even dreaming of a House of Representatives election at this time?
Later - It seems that the weekend polling results from The Asahi Shimbun, showing a switch in party popularity rankings among likely voters, drive a further stake into the heart of predictions of a snap House of Representatives election.
While these results are not definitive as to voter behavior in a House of Representatives election - voting for the House of Councillors tends to be more emotional and volatile, with voters tending to "punish" the party in power at the least provocation--seeing the DPJ rising to 29% while the LDP remains mired at 23% pretty much precludes the possibility of the PM calling a snap election.
One thing does seem certain: the non-aligned voter is back...and seemingly does not give a fig for Abe's idealist program. Abe and echo-chamber of advisors may have dreamt of completing the work of his grandfather as regards to restoring Japan to a prominent role in world power politics...or of building a better Japan through better Japanese. The non-aligned voter, however, sees these as peripheral and possibly even toxic.
Constitutional reform for the purpose of becoming a more
As for the middle-aged and the youth vote, it seems unlikely that educational reform emphasizing love of country and/or a constant chanting of "Racchi jiken" will disuade voters from their wish to kick the already wounded Abe in his shins.
Seriously who is going to turn down a chance to kick a weak, more-than-slightly-pompous rich kid when he is down?
Much later - Sorry, an earlier version of this post had a dropped "not" that rendered the argument unintelligible. The first sentence of the second paragraph the "Later" section now makes a bit more sense.