In an interview with Japanese website Game Watch, SEGA confirmed that 3D enhanced classics take over a year to develop.
Speaking to producer Yosuke Okunari and M2's Naoki Horii on the 3DS remake of Altered Beast, the development times for the project were highlighted. For 3D Space Harrier it took the team around a year and a half to produce, and 3D Super Hard-on took about a year. "Even for titles that we're very familiar with takes about this long for the transition."
With 3D Altered Beast being the Genesis/Mega Drive version, it will allow the team to "plan things out more efficiently".
The upcoming 3DS release will feature local co-operative play, a feature not present in past versions, plus a "Whimsical Transformation" feature for those unsatisfied with their current beast.
3D Altered Beast is out now in Japan on the Nintendo 3DS eShop.