One thing I like about DF is that its world is generated randomly with its own history and culture. Sort of alternate universes. The technology, if any, should follow the same suit.
Inventions, however, don't just happen at some time and suddenly enable all related developments.
Explosives already are available, just nobody has managed to develop safe and useful weapons from them. It takes a stroke of genius in random (nonetheless genial) person (dwarf) to discover a way.
However, the path from invention to actual development is still long, full of trial and error.
Dwarven inventors... now that is worth exploring. What would they come up with, would depend on available resources and circumtances they live within.
Lots of saltpeper and no hostiles in an area = no need for weapons = saltpeper is developed for economy. Nobody thinks of weapons until the necessity is there.
On other side, if the area is very hostile (kobold and goblin wars), dwarven inventors would seek ways to improve safety and gain an edge over enemies, so weapon development would be active. Again, it would depend on available resources; no saltpeter, no gunpowder, no muskets (unless different resource with similar properties is found).
There is no point inventing a boat within a vast desert... Except maybe if they are developed as 'dune boats' that ride the wind.
Dude, wait. THAT IS AWESOME.
Bring on the dwarven inventors!