Amazon.co.jp have recently listed the “Sonic the Hedgehog 4 Episode I/II Original Soundtrack” on their website, along with details of what will be contained on the single CD album.
The soundtrack will boast 54 tracks, including 23 songs from Episode I, 30 from Episode II, along with a final “bonus” song. While many tracks are expected to be jingles, this will be an opportunity for fans of the soundtrack to pick up a physical release, at the bargain price of ¥1890 ($25 / £16) which is cheaper than other Sonic-themed physical albums currently available.
The current scheduled Japanese release date is August 1st 2012. As of yet there is no indication to an EU or US release, or whether this album will be available to download through iTunes*.
Props to bsquared for the heads-up!
*EDIT: Jeffhog has just pointed out that these soundtracks have already been announced for digital release on the SEGA blogs.