sp story dlc only, not including vanity items, free equipment packs or day-1 dlc
ME
BDtS released 115 days after release, aprox. 16 weeks
PS released 533 days after BDtS, aprox. 76 weeks
ME2
Kasumi released 70 days after release, aprox. 10 weeks
Overlord released 70 days after KSM, aprox. 10 weeks
LotSB released 84 days after Overlord, aprox. 12 weeks
Arrival released 203 days after LotSB, aprox. 29 weeks
ME3
Leviathan released 175 days after release, aprox. 25 weeks
Omega released 91 days after Leviathan, aprox. 13 weeks
Citadel released 98 days after Omega, aprox. 14 weeks
DA
RtO released 59 days after release, aprox. 8 weeks
Awakening released 63 days after RtO, aprox. 9 weeks
Leliana's Song released 112 days after RtO, aprox. 16 weeks
GoA released 35 days after LS, aprox. 5 weeks
Witch Hunt released 28 days after GoA, aprox. 4 weeks
DA2
Legacy released 140 days after release, aprox. 20 weeks
Mota released 77 days after Legacy, aprox. 11 weeks
Exalted march was unreleased
DA3
JOH released 127 days after release, aprox. 18 weeks
Bioware average: 122 days between dlc releases, aprox. 17 weeks
DA team average: 80 days between dlc releases, aprox. 11 weeks
random observations: the first story dlc released almost always takes the longest, the number of sp dlc made available for sale is proportional to units sold
da:0@3.2 mill = 7 major sp story dlc
da2@1.3 mill = 2 major sp story dlc
inquisition is supposed to be Bioware's most successful game based on launch sales so fingers crossed and maybe we'll get more than 3?

so now that i've wasted a good 50 minutes of my life i'll never get back, i'm guessing warden dlc will be out late June/early July, egg hunt sometime after November
and that it will not give us full resolution because they're dicks like that