Update: It turns out that Sony Ericsson intends to continue working with DoCoMo by initially delivering new models through mid '08, at which point it will start buying handsets from other manufacturers and rebranding them. In other countries this would be truly egregious, but as our Japanese bureau points out, DoCoMo lays out very strict requirements for each of its lines that would probably make it difficult to distinguish a true Sony Ericsson model from a rebranded model sourced from, say, Sharp or Toshiba.
Update 2: Sony Ericsson's Japanese PR folks have denied Nikkei's report, although they did mention that they are "reevaluating" their DoCoMo line without going into any detail. Whether the report was actually false or Nikkei just managed to out the info well before Sony Ericsson wanted it out, though, remains unclear.
Update 3: The official Sony Ericsson response, and while it says that they're taking a good, hard look at their DoCoMo business, it also mentions that they'll continue to develop new handsets for the carrier. Clear as mud? Good!
Read - Nikkei report [subscription required]
Read - Sony Ericsson response