NASHVILLE (Billboard) - Initial ticket sales for the Dixie Chicks' upcoming tour are far below expectations and several dates will likely be canceled or postoned. Ticket counts for the 20-plus arena shows that went on sale last weekend were averaging 5,000-6,000 per show in major markets and less in secondaries, according to sources contacted by Billboard. Venue capacities on the tour generally top 15,000. In contrast, the band's new album, "Taking the Long Way," sold 526,000 units... Despite those numbers, early ticket sales are clearly not meeting projections. The plug was pulled on public on-sales for shows in Indianapolis (August...