I would agree. If you're not wheeling the big stuff, you don't really need dual cases. Having said that, dual cases are cool and a great mod if you're going to play in the rocks.
If/when you go to dual cases, re-tubing the drive shafts is the least of you're concerns... kind of an afterthought in a way. Purchasing the cases and adapters, getting them all built/attached and installed, working the cross member mounts, and fitting the sticks up in the center console is the part you have to think about most.
I wouldn't put off getting a good drive shaft made just because I might want duals down the road.
I'm outside your window watching you read this.