Final Fantasy V and VI Have 'Technical Issues' on DS wrote:Someone asked Hashimoto for an update on possible DS ports of Final Fantasy V and Final Fantasy VI. Hashimoto's response was "For FF5 and 6, there are technical issues as well, so at present these are also undecided."
He said "also" because a previous poster had asked about possible download release for Super Famicom's Seiken Densetsu 3. Hashimoto's response here was, "This is also at preset undecided."
(emphasis mine)
Original Twitter post by Shinji Hashimoto here (in Japanese).
Tech issues are probably cramming the games on a DS card. FF4 just about ate up the whole unit.
Also, it seems pretty specific about "download release" for Seiken Densetsu 3, so even if it does happen, it'll probably be on phones or Virtual Console, and neither of those methods will likely see a translation.