Development of the core game will be ongoing in parallel with the future paid expansions. That is why the development team has been made bigger.
Taken from last weeks development update:
Our first commitment is supporting the game with regular updates. This won’t just be the fixes and tweaking we’ve provided since release but will also add new features and content. Examples of this are Wings and associated multiplayer features, as well as the additional ships mentioned in recent newsletters. We’re proud of the fantastic game that we released before Christmas but intend to keep growing and developing it. To make this happen we’re expanding the team working on the game so that we can maintain a regular schedule of updates as well as working on paid expansions.
https://forums.frontier.co.uk/showthread.php?t=94899&highlight=
"DLC" as in
major paid expansions was "announced" more than two years ago during the Kickstarter. This is major new features to the game like planetary landings, first person gameplay on planets/stations/ships/EVA, having NPCs and other players as crew aboard your ship, executive control of capital ships, boarding other ships and so on...
These paid expansions is not the same thing as improvements to the core game that will be added to the game going forward. Things like more ships, "wings", improved and expanded missions, new space environments and stations, further improvements to combat/trading/exploration/mining...basically more of the depth people are asking for...these will still be free.