With most (if not all) of the E353 Series EMU have been delivered to the Matsumoto Depot, JR East has been converting its E257 Series EMU for the Odoriko serivce in the upcoming timetable revision and the first converted set (NA-09 from M-112) has been delivered from Nagano. Some of the known changes are that it is now E257-2000 Series and its home depot will be based on Omiya where it will replace the JNR Era 185 Series, any potential internal changes have not been revealed yet and not all the E257-0 Series will be converted as some will remain in Matsumoto to handle seasonal services (hence the numbering changes are not 1 to 1)
>>1294928From that article it seems like having the Shin-Tosu and Takeo Onsen section as single track doesn't really save that much money compared to dual track (540 billion Yen vs 620 billion Yen), but the delay is relatively minimal (51 minutes vs 55 from Hakata to Nagasaki)
