I'll be dramatically reducing my battle-mat usage, but there are some types of encounter that just scream for tactical positioning. Also, as the danger level ramps up, I want combats to be as transparent as possible. Minis and grid achieve both these things.
Of course it also depends on the quality/modularity of the rules, and what the players want. I've frequently been surprised by just how much my circle of roleplayers enjoys long, intricate, tactical engagements, so it may be that they draw the line in a different place than I do.
If DDN can truly achieve a drop-in tactical combat system to be deployed only when needed, it'll be a massive step forward for the game.