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Japan disaster relief now getting through to most survivors
Two vital things have improved for more than 250,000 evacuees still living in makeshift shelters a week after the Japan earthquake: supplies are getting through, and the weather has warmed up for now.

...The resilient character of the Japanese people has been on international display for the past week as this nation struggles to regroup from the 9.0-magnitude earthquake and tsunami that erased communities and gave a blow to the economy. For many evacuees, there is now nowhere to go, and Prime Minister Naoto Kan has warned that "life in the emergency refuge centers will continue for some time yet."

I think that much of the exigent housing problems will be solved through such expedients as opening up public housing, and the massive housing available from organizations such as Japan Post (in Japan, large companies generally have both a lot of company housing and even resort properties for their employees.) From the Yomiuri:

Japan Post offers rooms at inns
Japan Post Group has announced that it will offer inns and hotels operated by Japan Post Holding Co. as temporary houses for up to 22,000 people affected by the latest quake.
Japan Post will welcome displaced earthquake survivors to its inns and hotels in parts of the nation not hit seriously by the quake.
Specifically, 27 Kampo no Yado inns and hotels in Tokyo and 18 prefectures will be made available for about 4,700 people to live in, while 1,559 houses owned by Japan Post Network Co. and located at 30 places in Tokyo and 16 prefectures will also be opened to evacuees.
Regarding company-owned employee housing, which Japan Post had earlier intended to put out of use by the end of this month, there are plans to make available 2,872 houses at 66 locations in Tokyo and 16 prefectures, after they are repaired.

There are several reports in the Japanese press with long lists of municipalities donating public housing to those who have lost theirs.