Do shops restock ?

Well do they or could I just buy out everything and they would be empty for eternity ?

I don't believe they will restock on their own. However, since the only way to gain money in IVAN is by selling items TO the shops, there will always be things to buy...

...unless you manage to get your CHA above 100. IIRC, with 100 charisma, the cost to buy an item is equal to the cost to sell it.

Yes and since the shopkeepers have limited gold, you would never be able to sell enough to make enough money to buy them out. Well maybe with all the new worlds and shops, you could buy out the shopkeeper in New attnam

Yup once they're empty they stay that way. The original developers had plans to add an economics subsystem.
I guess once the shopkeeper sells all his stock, they get wealthy enough to book a permanent holiday...