I am at the point where there isn't anything I need to buy in Kuldahar so don't really need much more gold. Will the vendors in Kuld get more new items as I level or will I need gold for other vendors I find in the world later.

No specifics please as far as spoilers.

You didn't mention what chapter you're in, but some of Orrick's stock changes after Chapter two, if memory serves. And yes, there are other vendors later on that will offer different items. Keep gathering the gold, although you'll find at the end you'll still have plenty left over.

I keep finding better stuff than I could ever buy, but I'm only at the Dragons Eye so that could change.

Coelocanth is right that Orrick's inventory changes, i think his changes twice over the course of the game. However, other vendors in the game don't change their inventory.

I hope this isn't counted as a spoiler but when you start TOTLM (if you haven't already), the halfling has an infinite supply of certain items (won't say incase you consider it a spoiler ) worth dumping excess gold into. By that point in the game, you will already know what each store has and that won't change.