Deloitte said it expects revenues to climb 3.5 to 4 percent during the November-to-January holiday period. The gain represents a pullback from a 5.2 percent gain seen over the same period a year ago.

Daniel Bachman, Deloitte's senior U.S. economist, said sales should be supported by an improving labor market, increasing home values and lower gas prices.

“Housing and employment tend to create a more meaningful wealth effect than that of the financial markets, so the recent stock market fluctuations and instability overseas should not have a marked impact on shoppers' holiday spending intentions,” added Bachman. “However, while retail holiday sales are expected to rise, the increase may be smaller than last year due to the lingering effects of flat personal income growth in the first quarter.”

Overall, holiday sales from November through January are expected to climb to between $961 and $965 billion, up from $928 billion the prior year.

Deloitte also predicted an 8.5 to 9 percent increase in non-store sales in the online and mail order channels during the 2015 holiday season. The consulting firm said digital interactions – including both online and mobile engagement – will influence 64 percent, or $434 billion, of store sales this holiday season.

“Nearly 80 percent of shoppers say they engage with a retailer or brand through digital channels before setting foot inside the store,” said Rod Sides, vice chairman, Deloitte. “These interactions are retailers' opportunity to engage shoppers seeking inspiration, reviews, product locators, or the option to buy online and pick up in the store. Retailers that are likely to come out ahead this holiday season are the ones connecting the dots between their digital channels and their stores – rather than focusing solely on the online 'buy' button.”

Meanwhile, ShopperTrak predicted a 2.4 percent increase in sales during November/December holiday period. The location-based analytics firm said the trend toward shopping earlier will carry into the 2015 holiday season, as the split between November and December continues to narrow. An early Hanukkah also could produce a stronger surge in November sales.