Totally agree with these points. Now, we don't really know if those DLC are going to be released frequently or not, I'm expecting to see House of Wolves in February-March (although the latter would probably be a bad time for releasing it due to how cramped that month is), but after that we don't know if there are more expansions or not.
What I am expecting, if they do go forth with the "expansion" model, is to see the enemies of the Tower getting a DLC of their own, just like the Hive did with TDB with Eris, and the Fallen are getting with HoW with the Awoken Queen. We still have the Vex and the Cabal as well, we still haven't seen anything else from the Stranger, so one of those two expansions could have her as some kind of vendor I guess and some new character that we haven't seen yet.
At the end of the year, we get the so called "Comet" and that brings us more content, possibly new areas (Saturn, Mercury, Reef), and possibly an overhaul to everything, that will gear us up for Destiny 2 in 2016.