Hmmm...philosophy on a "gear head" discussion site.....worth the shot ;-)
Since a lot of readers hear are or claim to be "gear sluts", "gear whores" and all other manner of descriptors to justify their addiction to new shiny things, I would postulate that new gear will NOT make them happier. For a while, but once the "fix" wears off, it is on to something new to get the rush.
However, for some folks that are seeking tools that allow them to capture and translate what they envision or see to something in print or display with greater ease or control, then new gear may help them feel happier. Case in point.....if one shoots landscapes or travel images for example, then there are a couple of options.....those that just love fiddling with gear, making adjustments, and all the tinkering, and those that are able to get the shot they are imagining quickly and reliably to move onto the next thing. If your life is centered around the gear, then you will most likely never be really happy with whatever you have. If you center around other things, be it artistic expression, or even business success, then gear becomes a means to that end and not the end in and of itself.
So, would a shiny, fancy new camera and some super-duper fancy triaxial shifting lens make me happy? Only if it allowed me to get the shots that I envision easier and more frequently so that I could pursue those goals. If it just sits in the bag so that I can brag about it and polish it more than use it, happiness would be fleeting at best.
Anyway, just my thoughts on things. I will say that there would be a welcomed sense of joy, no matter how brief if I acquired some new, fun to use gear, but generating more income from clients by using that gear would be more satisfying, as it would allow me to pursue other things that bring fun and pleasure. (Different set of "needs", I guess, but good to have variety.)
LJ