When I first started driving a car on a track, there were lots of rich guys on the track with GT3s and 360 Stradales who had the same skills I did. I felt a need to upgrade my track car. A wise instructor told me, "When you reach the point where your car is holding you back, it is time to upgrade."
Basically, he was saying I should master driving in what I had to drive, before moving up. I had a cheap, but well prepared track car. I needed to outgrow it before even thinking about moving up.
Assuming you have a workable cooker, I think the same thing applies. If you can produce good BBQ on a 20-year-old kettle, then you will produce even better BBQ on a high end smoker. If the food you produce on that old kettle sucks, then buying a high-end smoker ain't going to do any good.
When you reach a point where your cooker is holding you back, lose it and upgrade. Or, if you are rich, just buy the Ferrari of cookers now, and fark up in style.