Almost every grape variety could be considered an "heirloom", as most have been around for over a millennium. At Kenneth Volk Vineyards, however, we're using the "rarity" definition rather than the "antique" one, to categorize rare varieties which we feel make remarkable wine (Malvasia, Trousseau, Negrette, etc.).
The popularity of the noble varieties (Chardonnay, Cabernet Sauvignon, Merlot, Pinot Noir, Reisling, Sauvignon Blanc) is understandable, as they have the track record of producing great wines in locations other than their championed homelands. The reality is that there are well over a thousand selections of Vitis Vinifera used for regional wine production in the old world.
Some of these varieties make interesting and memorable wines in isolated areas, but have lacked the promotion of the mass-marketed noble varieties to make it into the consciousness of the average wine drinker. Most of these heirloom rarities are considered "hand sell" marketing burdens in most channels of wine distribution; the mass consolidation of wine distributors and retailers has made it at best a novelty niche market.
That is not to say that rare, interesting grape varieties cannot be established in the marketplace. It took a long time for Viognier and Syrah to become part of the mass market consciousness. So why bother with hard to pronounce, obscure varieties? Our answer is that they can produce some delicious wines that have different flavor profiles than the mass-marketed chocolate, vanilla and strawberry standards. We take an advocacy position on these varieties, as they could face extinction if the market forces stay on the current path. It's a challenge, but it's fun and educational for us. In some ways, it's sort of like cross-training, and gives us insight into making better wines in general.
What can you expect in the future in heirloom varietals? How about Malvasia, Mourvedre, Negrette and Tempranillo for starters?