Titanfall's attach rate on Xbox One is still significantly higher than Destiny's attach rate on PS4. So it's not quite as impressive imo. Now Destiny's attach rate on PS4 could catch up to Titanfall's attach rate on Xbox One, but I'm not convinced that it will, not after the lukewarm critical reception that Destiny received, that could hurt it's legs.
Uh, of course it won't.
Think about when Titanfall was released. Both PS4 and XB1 had very few flagship games (no Halo, no Gears, no God of War, no Uncharted, no Gran Turismo, etc/infinity).
Titanfall was launched during drought-times, given away with XB1 WITH a discount, etc. The attach rates were high for these reasons, and of course the biggest hype train and advertising blitz I've ever seen in 3+ decades of gaming.
Now compare a game like GTAV's attach rate to Titanfall. GTAV looks like an absolute failure by comparison, the attach rate was never even close to Titanfall even after so long on the market. Yet GTAV is a resounding success.
Destiny has done, and will do quite well, but it's also launching at the beginning of the fall season, so it's going up against an incredibly diverse lineup of titles rather than a drought.
If Destiny had launched in March of this year? I think the attach rate would have been similar. Basically you could swap either of these games out and get the same result. Titanfall launched in September at $59 and no free + discounted packin bundle, attach rates wouldn't be nearly what they were by launching in March.