I have not looked at the next Playtests for quite some time, so I'm not particularly well-informed on this topic. That said, this is the internet, so here are my incredibly poorly informed thoughts.
Of course dwarves, halflings, and probably gnomes should be slower than the bigger races. That said, the mechanical effect really depends on what kind of game we are playing. If the game is entirely theatre of the mind, there shouldn't be any mechanical effect. Let the dwarf's player describe his character as red-faced and panting as he chugs along to keep up with the long-legged ranger. Let the half-orc barbarian's player describe himself as hoisting the halfling burglar up by his underpants as he charges across the battlefield. In combat, the slower races, in my opinion, should move from long to medium to short to melee ranges without any mechanical differentiation from their faster counterparts.
If we're playing out a complicated tactical situation on a grid, though, this all changes. The halfling, dwarf, and gnome should move 4 squares (or whatever), while everyone else moves 5 or 6. As a caveat, I picture gnomes as forest-dwellers who are shy about the larger races, so while slower than the lon-legged types, maybe they should have a racial ability that lets them move through difficult, forested terrain without penalty.