Apparently, Docomo announced on April 28 during the third quarter earnings report that the Xperia is getting i-mode mail in September followed by an update to the 2.1 eclair in October. I guess I haven't been paying attention these days. (Thanks for the tip, Ahmed!)
I have heard no updates about when HTC will release 2.1 firmware for the magic (ht-03a) - it appears to still be scheduled for this summer. From this ridiculously cluttered slide I found at IT Media, it appears that the only smartphone that will get a docomo cell phone email address is the Xperia.