A
amerigoV
Guest
God, you would have to rewrite the macro system, create lobbies, integrate the thing into a "gamers seeking gamers" website, make it compatible with Character Builder and Monster Builder, make it compatible with the Compendium....
This is not "obvious." Programming is hard, it costs a lot, and would people really pay that much more for DDI to make this worthwile for Wizards? Would you pay 3 Dollars more a month?
If done right, I would pay extra. Done right = the integration with the tools you mention (ie, straight from those tools to a token on your map). I would love it if you pulled up an adventure in Dungeon (or input a code for one you bought) and just pushed a button to launch the VTT and it was all set (LoS, FoW, and descriptions all ready to go on the maps that comes with it).
The issue now is the other solutions out there are getting really good at nominal to small cost. They likely have missed the boat to viably do this for 4e (if you wanted/needed a VTT, you probably are already using MT/FG2/etc).