A'koss said:
Sounds like "Ye Olde Magic Shoppes" will be alive and well in 4e.
The game rules don't dictate the presence of magic shops. Not very much, at least. The fact that items have prices does not imply that there are stores where you can buy them wholesale. The prices might be the amounts you would have to pay an obscure collector and purveyor of magical rarities for the one and only Boots of Bountiful Buckles in existence. Or not. That's really setting dependent, and up to the individual game.
Everyone claims that 3e created a magic item shop effect, but it really didn't. At least not much.
The only way the rules encourage magic item shops is this (and this is edition independent as long as all the following is true):
1: PCs need a certain amount of magical gear to fight battles of the level they typically encounter. (True in 4e, though less than it was in 3e.)
2: PCs obtain a significant portion of their magical gear from random monster drops generated from a table and a percentage dice. (This is a very DM specific thing. Some DMs use the treasure tables, others ignore them. This is probably equally true in 4e as it was in 3e.)
3: Not all magical gear is equal, or at least not all of it is equal in the eyes of the PCs. (This is probably true in 4e. Magical wizard implements do no good if you haven't got a wizard.)
4: A large portion of the character's power level is in consumable magical items, which must be replenished. This can be potions, or even arrows. (I expect this to be less true in 4e than it was in 3e, due to the desire to avoid too much bonus stacking.)
This creates a situation where the characters have plenty of magical items, but they don't have the right ones. If you want them to function, there has to be a way to convert magical items they don't want into magical items they do want. Enter Ye Old Magick Shoppe, stage left.
As long as the above is true, you will find the need for magic item shops. Change the above, and you need them a lot less. Stop doing random drops, for example, and start customizing magical item rewards, and there's suddenly no major need for a magic item shop. Find a way to handle between-combat healing, and suddenly there's less need for potion shops. Et cetera.