I can't see a new Dragon Age being releasing before 2017-2018.

-Bioware Edmonton is a 2 or possibly 3 team studio. One team has been working on a new IP for almost a year now, another just finished DA: I, and a possible 3rd team may have been working on a Star Wars game since EA acquired the Star Wars license in June 2013. So they'll likely be busy for a few years with games other than Dragon Age, unless the DA: I team goes straight to work on a new Dragon Age.

-Bioware Montreal is a 1 team studio as far as we know, and they are currently working on Mass Effect 4, which releases in 2016. That means that they won't be starting development on a new project until ME4 is released, so assuming 2-3 years of development, their next game after ME4 probably won't release until 2018-2019.

-Bioware Austin is a 2 team studio as far as we know. 1 team is still developing new content for SWTOR, and the 2nd team was working on Shadow Realms up until it's cancellation. We don't know what the former Shadow Realms team will be working on next, it could be Dragon Age but I doubt it. Maybe Bioware Edmonton will hand the rumored singleplayer Star Wars game over to them, since they already have experience working on Star Wars thanks to SWTOR, and Bioware Edmonton will develop the 2 new IP's.

Agreed, they definitely need to release it before ME4, and preferably not in the same year as ME4, which means they should release it before the end of this year. I'm guessing that it wouldn't take a very big team to do it though, I'd think that a 20-30 man team could have it ready for release by Holiday 2015 if they started on it now. Maybe a subset of the 200 man ME4 team at Bioware Montreal will break off and do the ME HD collection. Or maybe that was why Shadow Realms was cancelled, maybe Bioware decided to have that team make the ME HD Collection.