For quite a while, one of the main criticisms of R&D's handling of the design of red cards was that they relied too heavily on one divisive creature type: Goblins. These were, of course, the main type for small red creatures throughout Magic's history. Fans love their tribal interactions (long a strength of red aggro) and comic relief flavor, and detractors dislike their linearity, overuse, and... comic relief flavor. The latter group still longs for the days of at least slightly more serious red creatures like Orcs and Dwarves. But while recent blocks have, surprisingly, replaced Goblins entirely with Innistrad's Devils and Theros's Satyrs, the Tolkienesque Orc and Dwarf types have long been gone.
But, apparently, that's about to change. Mark Rosewater recently answered questions about these creatures in a hopeful light on his Tumblr blog.
When magictheflavoring asked, "Will orcs return one day? I know they're perhaps too synonymous with Lord of the Rings, but Dungeons and Dragons uses them, too..." Rosewater replied:
Fear not. I highly doubt we’ve seen the last of our orcs.
This is an oddly confident answer given the last time an Orc was in an expert-level expansion was almost ten years ago; but the appearance of certain Khans of Tarkir warlords suggest they may be in the upcoming block.
Meanwhile, when waxingnostalgicforthe90s asked, "Why were Dwarves blacklisted by R&D?" he responded:
I don’t know. We just had a few anti-dwarf people. The good news is I think most of those people are gone so dwarves might resurface one of these days.
Dwarves did show up in Eventide for one brief shining moment as the Tommyknocker-esque Duergar, but not since then. When the shortlisted "underground block" gets made, however, Dwarves are a shoo-in with the doubters out of R&D.