A three-year inventory has dropped to a two-year supply in the tri-county area, indicating that the market might be poised for something of a rebound. Jack McCabe, a Deerfield Beach-based analyst who for several years has predicted doom for the housing market here, called this a positive indication for the regional market. That’s not to say all is well. Palm Beach County sellers listed 31,020 houses and condos for sale in August, a month when only 1,122 homes sold, according to research firm Trendgraphix. Brokers say a six-month supply of existing homes is normal, so today’s 28-month supply is far from healthy.